Depends on the device, but there some (albeit old ass phones) that run it fairly stable. That said, I think the closest, newest phone is the still capable OnePlus 6
You can use Waydroid to run Android apps. I would strongly recommend that anyone using Postmarket OS should also use F-droid apps as there is decent selection with lots of privacy tools.
Peertube really has three big problems. The first problem is that federation is kind of broken so it is hard to find content. The second problem is that running a server is very expensive. The third and final problem is that Peertube is way to French focused. They need to target a bigger audience and have English as the primary language especially for the big instances.