I’m on LineageOS since 2016, something may have changed but I usually look up their supported hardware and pick a phone based on that. You may have to look at something relatively recent or you could end up meeting the end of their official support, which then goes into some les reliable unofficial support by random people you can find mostly on XDA.
Personally I’m looking next to a second hand Pixel, mostly out of curiosity.
Edit: forgot to address the “why”: to keep in touch with society without letting strangers access to my stuff.