The Sangha extinguished, the Dhamma sold out: what now?

Listen to The Lion:

The Lion - Sīha Sutta (AN 4:33)

“Monks, the lion, the king of beasts, leaves his lair in the evening. Having left his lair, he stretches himself. Having stretched himself, he looks all around the four directions. Having looked all around the four directions, he roars his lion’s roar three times. Having roared his lion’s roar three times, he heads out for game. Any animals who hear the sound of the roar of the lion, the king of beasts, for the most part feel fear, terror, & fright. Those who live in holes go into their holes. Those who live in the water go into the water. Those who live in the forest go into the forest. Birds flee to the air. Even royal bull elephants, bound by strong leather bonds in villages, towns, & capital cities, bursting & breaking their bonds, frightened, scattering their urine & feces, run to & fro. So powerful among animals, monks, is the lion, the king of beasts—so mighty & majestic.

“In the same way, monks, when a Tathāgata appears in the world—worthy & rightly self-awakened, consummate in clear-knowing & conduct, well-gone, an expert with regard to the cosmos, unexcelled trainer of people fit to be tamed, teacher of devas & human beings, awakened, blessed—he teaches the Dhamma: ‘Such is self-identification, such is the origination of self-identification, such is the cessation of self-identification, such is the practice leading to the cessation of self-identification.’1 Any devas who are long-lived, beautiful, abounding in pleasure, established for a long time in high palaces, on hearing the Tathāgata’s Dhamma, for the most part feel fear, terror, & fright: ‘Being inconstant, it seems, we supposed we were constant! Being impermanent, we supposed we were permanent! Non-eternal, we supposed we were eternal! We—inconstant, impermanent, & non-eternal, it seems—are encompassed in self-identification.’ So powerful in the world with its devas, monks, is the Tathāgata—so mighty & majestic.”

...

Note

1. See MN 44.

It's hard to imagine that there is any valid and not actually defeat group of monks

Is a reason for the Sangha so that you can confess to each? I imagine that implies a little humility and forgiveness, of moments of heedless and behaviour and even of views.

And you tagged the question mahayana, the Bodhisattva Precepts include

6. Not to broadcast the misdeeds or faults of the Buddhist assembly, nor encourage others to do so.
7. Not to praise oneself and speak ill of others, or encourage others to do so.

What to do if getting clear that their is no more refuge to be found?

Refuge is in the "Noble" (arya) Sangha.

AI will soon be, or is already, your only 'friend'.

You wrote this in the context of "Dhamma being sold out" -- but that is a topic or theme about which you seem perennially hostile -- and so perhaps this is a topic or subject which, instead of discussing, it is better to let go of (like you might avoid any "fetter of views", and pacify hostility with non-hostility).

As for "friend", I don't know. I read that monks are not supposed to address each other as "friend", so, do monks have friends?

Something I read long ago, from a non-Buddhist source -- "To have a friend you need to be a friend."

So if not having friends seems like a problem, maybe you can find or make opportunities to be a friend, occasionally.

What should one go after

Well "going after" might imply craving, and "want to get off" craving too (vibhava-taṇhā).

There is "laying down the burden" as an end, and "absence of remorse" as a basis:

• Kimattha Sutta: What is the Purpose? (AN 11.1)

And "absence of remorse" is founded on "skilful ethics".

I'm not sure what "skilful ethics" means for a monk? Does it only mean following the Vinaya to the letter? Perhaps the Vinaya isn't everything, in that the original Sangha didn't have "rules", and the rules were introduced as necessary, case-by-case.

So perhaps there's more to it, a way of working (together), a (shared) purpose, a goal, apart from the rules which are maybe peripheral.

Might "ethics" be occasioned by friendship? An example of ethical behaviour, for which in retrospect there's no remorse, is to "do right by" a friend.

There's a sutta -- cited here -- which says that when the "heart is possessed and overwhelmed by" the hindrances, then you can't see, but that

a man dwells with his heart not possessed, not overwhelmed by sense-desires... ill-will... sloth-and-torpor... worry-and-flurry... doubt-and-wavering... [like the five bowls of water not as previously described, but 'clear, limpid, pellucid, set in the open']... then he knows and sees, as it really is, what is to his own profit, to the profit of others, to the profit of both himself and others. Then even sacred words he has not long studied are clear to him, not to mention those he has studied.

... and perhaps that's a definition of "skilful ethics".

So Ananda live as your own island, your own refuge, with no other refuge. Let the teaching be your island and your refuge, with no other refuge.

Tasmātihānanda, attadīpā viharatha attasaraṇā anaññasaraṇā, dhammadīpā dhammasaraṇā anaññasaraṇā.

DN 16

People follow & associate for a motive. Friends without a motive these days are rare. They're shrewd for their own ends, & impure. Wander alone like a rhinoceros.

Snp 1.3