I've been building Limit Phone. It uses MDM to manage your own Android device and block apps and websites at lower level than most other blockers.

It comes with a custom build of firefox so you can allowlist wildcards e.g. youtube.com/watch?v=* so you're not blocked from individual youtube videos which are much less harmful than the algorithmic feeds.

Me and a few friends are using it and it's surprisingly robust since it gets in your way a lot less (you can also set it up so you can temporarily bypass stuff after a delay)

It's still pretty new, it hit beta a couple of months ago! I'm working on making it more customizable and making the install process easier.