- Unlock bootloader (depending on vendor, you have to do an online verification),
- flash a recovery.img,
- load into recovery mode (which, depending on the phone, might need extra work)
- wipe some caches,
- select new os/rom image,
- pray it doesn’t brick your phone.
You’d think someone would’ve learned a thing or two from the easy graphical installations linux and even windows have been offering since the late 2000s.
But then everyone’s pc was built somewhere by someone. Smartphones could use the same model. It would improve competition between specialised parts manufacture, premade units could be priced according to the sum and performance of their parts, ewaste reduction when people can upgrade only the part they want. There is a lot of consumer upside whether you build or buy premade.