Other physical (samatha) meditation objects besides breath?

As Ayya Khema writes, on "body sweeping" meditation for absorption:

Whoever was able to have pleasant feelings in the body can use these feelings as the subject of meditation. One doesn’t necessarily have to go through the whole of the body as we have just done, but the moment the pleasant feeling arises in the body, these sensations become the subject of meditation. That constitutes the initial step toward the first meditative absorption, being one aspect of it. It is, of course, much easier to become absorbed in something pleasant than in a rather neutral feeling, so this enables a meditator to bring sustained application to the subject of meditation. Then all five factors of the first meditative absorption become possible. It doesn’t matter whether the whole body or just parts of it are filled with the pleasant feeling, because it is the sensation that matters as the subject of meditation.

Ajahn Brahm writes:

there are many other objects of meditation: loving-kindness (mettā), parts of the body (kāyagatāsati), simple visualizations (kasiṇa), and others. However, in all meditation that develops into jhāna there must come a stage where the pīti-sukha born of letting go arises. For example, loving-kindness meditation opens into a wonderful, gorgeous, unconditional love for the whole cosmos, filling the meditator with delicious joy. Pīti-sukha born of letting go has arisen, and one is at the stage of “beautiful mettā.” Some meditators focus on parts of the human body, often a skull.

Two related books, the first is a free ebook:

The Fire Kasina https://firekasina.org/2017/11/27/the-fire-kasina-book-by-shannon-stein-and-daniel-m-ingram/

Practicing the Jhanas: Traditional Concentration Meditation as Presented by the Venerable Pa Auk Sayadaw https://www.amazon.com/dp/159030733X

Buddhaghosa uses "kammatthana" to refer to each of his forty meditation objects listed in the third chapter of the Visuddhimagga, which are partially derived from the Pāli Canon.[2]

https://en.wikipedia.org/wiki/Kamma%E1%B9%AD%E1%B9%ADh%C4%81na

yes, when it comes to rupa, there is bhāvana on ''rupa'', or better said, bhāvana on each one of the five properties http://obo.genaud.net/dhamma-vinaya/ati/mn/mn.062.than.ati.htm#p1

"How, lord, is mindfulness of in-and-out breathing to be developed and pursued so as to be of great fruit, or great benefit?"

"Rahula, {any form whatsoever that is past, future, or present; internal or external; blatant or subtle; common or sublime; far or near: every form is to be seen as it actually is with right discernment as: 'This is not mine. This is not my self. This is not what I am.'

There are these five properties, Rahula. Which five? The earth property, the water property, the fire property, the wind property, and the space property.

"And what is the earth property? The earth property can be either internal or external. What is the internal earth property?}[3] Anything internal, within oneself, that's hard, solid, and sustained [by craving]: head hairs, body hairs, nails, teeth, skin, flesh, tendons, bones, bone marrow, kidneys, heart, liver, membranes, spleen, lungs, large intestines, small intestines, contents of the stomach, feces, or anything else internal, within oneself, that's hard, solid, and sustained: This is called the internal earth property. Now both the internal earth property and the external earth property are simply earth property. And that should be seen as it actually is present with right discernment: 'This is not mine, this is not me, this is not my self.' When one sees it thus as it actually is present with right discernment, one becomes disenchanted with the earth property and makes the earth property fade from the mind.

"And what is the water property? The water property may be either internal or external. What is the internal water property? Anything internal, belonging to oneself, that's water, watery, and sustained: bile, phlegm, pus, blood, sweat, fat, tears, oil, saliva, mucus, oil-of-the-joints, urine, or anything else internal, within oneself, that's water, watery, and sustained: This is called the internal water property. Now both the internal water property and the external water property are simply water property. And that should be seen as it actually is present with right discernment: 'This is not mine, this is not me, this is not my self.' When one sees it thus as it actually is present with right discernment, one becomes disenchanted with the water property and makes the water property fade from the mind.

"And what is the fire property? The fire property may be either internal or external. What is the internal fire property? Anything internal, belonging to oneself, that's fire, fiery, and sustained: that by which [the body] is warmed, aged, and consumed with fever; and that by which what is eaten, drunk, chewed, and savored gets properly digested; or anything else internal, within oneself, that's fire, fiery, and sustained: This is called the internal fire property. Now both the internal fire property and the external fire property are simply fire property. And that should be seen as it actually is present with right discernment: 'This is not mine, this is not me, this is not my self.' When one sees it thus as it actually is present with right discernment, one becomes disenchanted with the fire property and makes the fire property fade from the mind.

"And what is the wind property? The wind property may be either internal or external. What is the internal wind property? Anything internal, belonging to oneself, that's wind, windy, and sustained: up-going winds, down-going winds, winds in the stomach, winds in the intestines, winds that course through the body, in-and-out breathing, or anything else internal, within oneself, that's wind, windy, and sustained: This is called the internal wind property. Now both the internal wind property and the external wind property are simply wind property. And that should be seen as it actually is present with right discernment: 'This is not mine, this is not me, this is not my self.' When one sees it thus as it actually is present with right discernment, one becomes disenchanted with the wind property and makes the wind property fade from the mind.

"And what is the space property? The space property may be either internal or external. What is the internal space property? Anything internal, belonging to oneself, that's space, spatial, and sustained: the holes of the ears, the nostrils, the mouth, the [passage] whereby what is eaten, drunk, consumed, and tasted gets swallowed, and where it collects, and whereby it is excreted from below, or anything else internal, within oneself, that's space, spatial, and sustained: This is called the internal space property. Now both the internal space property and the external space property are simply space property. And that should be seen as it actually is present with right discernment: 'This is not mine, this is not me, this is not my self.' When one sees it thus as it actually is present with right discernment, one becomes disenchanted with the space property and makes the space property fade from the mind.

"Rahula, develop the meditation in tune with earth. For when you are developing the meditation in tune with earth, agreeable and disagreeable sensory impressions that have arisen will not stay in charge of your mind. Just as when people throw what is clean or unclean on the earth — feces, urine, saliva, pus, or blood — the earth is not horrified, humiliated, or disgusted by it; in the same way, when you are developing the meditation in tune with earth, agreeable and disagreeable sensory impressions that have arisen will not stay in charge of your mind.

"Develop the meditation in tune with water. For when you are developing the meditation in tune with water, agreeable and disagreeable sensory impressions that have arisen will not stay in charge of your mind. Just as when people wash what is clean or unclean in water — feces, urine, saliva, pus, or blood — the water is not horrified, humiliated, or disgusted by it; in the same way, when you are developing the meditation in tune with water, agreeable and disagreeable sensory impressions that have arisen will not stay in charge of your mind.

"Develop the meditation in tune with fire. For when you are developing the meditation in tune with fire, agreeable and disagreeable sensory impressions that have arisen will not stay in charge of your mind. Just as when fire burns what is clean or unclean — feces, urine, saliva, pus, or blood — it is not horrified, humiliated, or disgusted by it; in the same way, when you are developing the meditation in tune with fire, agreeable and disagreeable sensory impressions that have arisen will not stay in charge of your mind.

"Develop the meditation in tune with wind. For when you are developing the meditation in tune with wind, agreeable and disagreeable sensory impressions that have arisen will not stay in charge of your mind. Just as when wind blows what is clean or unclean — feces, urine, saliva, pus, or blood — it is not horrified, humiliated, or disgusted by it; in the same way, when you are developing the meditation in tune with wind, agreeable and disagreeable sensory impressions that have arisen will not stay in charge of your mind.

"Develop the meditation in tune with space. For when you are developing the meditation in tune with space, agreeable and disagreeable sensory impressions that have arisen will not stay in charge of your mind. Just as space is not established anywhere, in the same way, when you are developing the meditation in tune with space, agreeable and disagreeable sensory impressions that have arisen will not stay in charge of your mind.