Degoogle Android, Actually quite easy to bring back google service. I'm using the Chinese-version vivo x200p, the most troublesome is having to put app in enery-intense mode if you want them to run in background, or else the OS will kill them if they are unused for a while.
HarmonyOS NEXT, which is the only serious viable alternative to ios or android
Which is a microkernel based OS, with a userspace based on ArkTS, C, C++ and eventually Cangjie.
Quite interesting for us OS nerds, less so for those that only care about UNIX on their phone.
Mostly just de-googled android
Huawei's HarmonyOS is quite good. As for other brands like OPPO and Xiaomi, I've used them before too. You can use Google Play and a whole range of Google apps, but the localization adaptation is much better.