Not a fan of ColorOS but like the Realme X? Well, Realme has been actively encouraging community developers to build custom kernels and ROMs for the device. The project has born fruit after just a month, with there now being many Realme X custom ROMs and an AOSP-compatible kernel.
https://www.notebookcheck.net/The-Realme-X-is-an-example-of-community-development-done-right.440602.0.html