I've replaced batteries in a handful of newer smartphones. It's certainly more of a pain in the rear than on devices who's batteries were meant to be swappable, but it's still do-able. iFixit has parts, guides, and difficulty ratings for a lot of devices.
https://www.sustaphones.com/ has a list of Android devices with up-to-date community ROMs and iFixit battery replacement guides.
https://www.sustaphones.com/ has a list of Android devices with up-to-date community ROMs and iFixit battery replacement guides.