Did miracles stop after the Prophet peace be upon him?
Miracles continue after the Prophet peace be upon him except that they can no longer be used to claim prophecy.
Miracles by prophets are called mu’jizaat. When it occurs to regular Muslims they’re called karamaat.
Karamaat can be discussed but preferably privately while one is still alive, as opposed to mu’jizaat which should be publicized so people can know about that prophet. In general, karamaat happen outside one’ will, whereas prophets can intentionally perform miracles. But there are examples of the opposite happening on both sides.*
Karamaat indicate that the person was sincere to Allah at that moment. It does not mean anything more such that they are correct about everything in deen or in action or that they can just coast from here on in or that they are guaranteed Paradise. This is important because one of the tricks of Shaytan is to link miracles with correctness in all other things, and thereby confusing you when opposing groups all claim miracles.
Miraculous happenings can occur for non-believers out of His mercy, not His approval of their beliefs/actions. The Quran states, “It is He who answers the desperate when they call.” He left it open and did not say the desperate Muslims only. Allah’s mercy of Al-Rahman extends to all creation. His name Al-Rahim is a more subtle, hidden, inner mercy that extends only to believers.
When miracles happen to people who are openly doing evil, it’s istidraaj, which is leading them further onto the path of evil they insist on taking, despite having been warned.
*Jurayj the monk was not a prophet yet performed a karamaa willingly to prove his innocence, and the fire of the Majus went out when the Prophet peace be upon him was born without him willing it.