I’m sure this won’t gain that many votes, but the Vibe X3 is an unfairly forgotten device by Lenovo with Fantastic speakers and audio quality in headphones. Unfortunately, this device does not have LineageOS or any officially supported custom ROM. All there is is one actively supported repo and a few more with not much to find:
Look for shayankewl’s contributions as well for a vendor of the Vibe X3.
The official firmware is very poorly optimized and while it is possible to get microG running on it, the experience is very buggy. Perhaps, the links above could be of any use to get a build for this device?