- 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.
I have been tweaking my phone ever since Nexus 3 age. And only recently settle in the default MIUI/HyperOS and that is only after unlocking and removing a bunch of bloats.