If I was up late despite knowing fajr was near I slept woke up at the early time of fajr, set a timer to wake up later despite knowing I could oversleep, and I overslept fajr. Is this leaving salah intentionally as some scholars consider this kufr. I woke up late prayed and did tawbah immidiately.

Ustadh AbdulAziz al-Haqqan

It is a grave sin and you should not do that again. Once you wake up, you pray. If staying up is going to make you miss the prayer, then it is forbidden for you to stay up late.