Was Simon who hosted Jesus in Lk 7, Mk 14 and Matt 26 one and the same person?

The Simon who hosted Jesus at the dinner recorded in Luke where Mary anointed Jesus' feet is the same Simon who had formerly been a leper as recorded in the accounts of Matthew and Mark. This fact adds to his guilt in not being understanding of Mary's actions, for he himself had been a great sinner whom Jesus had cleansed and healed of his leprosy--and it was his spiritual blindness on this point that prompted the response of Jesus we see recorded in Luke.

Notice Simon's own words (thoughts) at that dinner:

Now when the Pharisee which had bidden him saw it, he spake within himself, saying, This man, if he were a prophet, would have known who and what manner of woman this is that toucheth him: for she is a sinner. (Luke 7:39, KJV)

Consider: How did Simon know what Mary had done?

Simon had been healed, but Mary had been forgiven. Jesus admonished Simon gently, after Judas, who had started the criticism of Mary which Simon afterward reflected, had left. This he did in the form of a parable of two forgiven debtors (as recorded in Luke's account), asking which one would love the creditor most. Simon answered correctly, but still, as a proud Pharisee, was unable to see himself as he truly was. He considered himself to be far greater than Mary, and seeing how Jesus had accepted her devotions, his respect of Jesus had been lessened.

There is considerable congruity among the several accounts of this event. Two of them specify that Simon had been a leper, and the third, addressing him as a Pharisee, still names him as Simon.

Now when Jesus was in Bethany, in the house of Simon the leper, (Matthew 26:6, KJV)

And being in Bethany in the house of Simon the leper, as he sat at meat, there came a woman having an alabaster box of ointment of spikenard very precious; and she brake the box, and poured it on his head. (Mark 14:3, KJV)

And he turned to the woman, and said unto Simon, Seest thou this woman? I entered into thine house, thou gavest me no water for my feet: but she hath washed my feet with tears, and wiped them with the hairs of her head. (Luke 7:44, KJV)

All three mention the alabaster box (and these are the ONLY mentions of an alabaster box in the entire Bible), which, in all three, contained ointment.

There came unto him a woman having an alabaster box of very precious ointment, and poured it on his head, as he sat at meat. (Matthew 26:7, KJV)

And being in Bethany in the house of Simon the leper, as he sat at meat, there came a woman having an alabaster box of ointment of spikenard very precious; and she brake the box, and poured it on his head. (Mark 14:3, KJV)

And, behold, a woman in the city, which was a sinner, when she knew that Jesus sat at meat in the Pharisee's house, brought an alabaster box of ointment, (Luke 7:37, KJV)

The alabaster box alone gives strong evidence to the story all being one and the same. Were it not the same, there would have been two separate occasions when a woman and/or Mary had anointed Jesus' feet with ointment. But if this had been the case, there is no indication of it in the Gospels. And why would such an occurrence have taken place twice under virtually the same circumstances and in the house of a man of the same name?

Matthew focuses on Judas' accusations of Mary's wasteful extravagance.

Mark goes further in stating a possible price of that extravagance.

Luke focuses on the Pharisee's unjustified pride, yet without shaming him as a former leper, or mentioning the specifics of his guilt. (It's worth pondering the fact that at the time these accounts were written, their subjects were most probably yet alive.)

Conclusion

The evidence is undeniably strong in support of the three separate accounts pointing to the same event. As is usual with stories found in the Gospels, each account of the same event may be presented with the unique focus of that particular writer.

The account described in Luke chapter 7 clearly identifies the host as Simon, a Pharisee. As you have rightly pointed out, the host should have offered Jesus water to wash his feet. Instead, it fell to a sinful woman to weep over Jesus’ feet, dry them with her hair, then anoint them with expensive perfume. The self-righteous Pharisee, who invited Jesus, thought ill of Jesus for allowing this to happen. Note, he did not make any audible accusation against Jesus, but Jesus knew his thoughts.

My NIV Study Bible (Protestant) says the motivation of the Pharisee who invited Jesus to have dinner with him may have been to entrap Jesus rather than to learn from him. With regard to the woman who had lived a sinful life, the NIV comments say this:

A prostitute. She must have heard Jesus preach, and in repentance she determined to lead a new life. She came out of love and gratitude, in the understanding that she could be forgiven. Jesus reclined on a couch, with his feet extended away from the table, which made it possible for the woman to wipe his feet with her hair and still not disturb him. The anointing, perhaps originally intended for Jesus’ head, was instead applied to his feet. A similar act was performed by Mary of Bethany just over a week before the crucifixion (John 12:3).

Let us now turn our attention to Simon the Leper, which account is recorded in Mark 14:3-9 and also in Matthew 26:6-13. Here is an extract from a Protestant article:

While Jesus was staying in Bethany, one night He and the disciples were invited for a meal at the home of Simon the Leper. As Jesus reclined at the dinner table, an unnamed woman came in, broke an expensive flask of perfume and poured the oil over the Lord’s head, anointing Him in an extravagant act of worship. The disciples reacted with indignation at the woman’s waste of valuable resources. But Jesus told them to leave the woman alone, “for she has done a beautiful thing to me” (Matthew 26:10, ESV). Her anointing was a fitting way to honor the Messiah-King and prepare Him for burial. This dinner at Simon the Leper’s home took place about one week before Jesus was crucified.

Similar but distinct episodes are featured in Luke 7:36–50 and John 12:1–8. The event in Luke transpired at the home of a different Simon, “Simon the Pharisee,” with a woman referred to as only “a sinner.” The event in John happened on a different day and involved Mary of Bethany. Source: https://www.gotquestions.org/Simon-the-leper.html

Please be aware that Simon was a very common name in New Testament times, and at least eight men bearing that name appear in the Bible. It is also possible that Jesus healed Simon the Leper.

It is my understanding that the events recorded in Luke’s gospel happened before Jesus’ triumphal entry into Jerusalem and the last supper he shared with his disciples. Luke's account of Simon the Pharisee seems to happen after the calling of Levi, the beatitudes, the faith of the centurion whose servant Jesus resurrected and the raising of the widow's son. The events described in Mark and Matthew’s gospels happened only a few days before the last Passover.

Also, the events at the home of Simon the Leper involved Jesus’ head being anointed, whereas the event that took place at the home of Simon the Pharisee involved Jesus’ feet being anointed. It is also difficult to imagine how a former unclean leper could have also been a Pharisee.

Conclusion: Simon the Pharisee is a different Simon to the former leper who lived in Bethany.