While adding ROMs to the Pixel line (if unlocked) is pretty easy, however other Android phones is usually a nightmare and only geeks will ever attempt it. I only did it because of EOL android phones. I gave up about 3 years ago and just got an iPhone. I do still have an Pixel 3 with CalyxOS on it tho. I like the hackability of android, but it's just not worth it. I just don't like mobile hacking, I do that with my desktop, pi's, and various embedded boards that are much more open to fun hacking.