Running FP4 myself, bought bit less than a year ago. If I can get it last significantly longer than phones usually do, I get another one. If not, I have to come up with something else.
No complaints so far but I do all the fancy stuff on PC so I don’t need much from my phone. Remains to be seen if it’s worth it.
Some fork of youtube-dl would probably do. Personally I use JDownloader 2 (open source) to download not just from youtube but from any other sites as well. It runs locally.