I can’t (yet) build customROMs, but I can install GSI. And the advised /e/OS-T GSI could be a (partial) solution, because I was able to modify the Xiaomi Redmi firmware to run a current GSI Lineage-20.0-20240516 from @AndyYan on my Redmi Note 6 Pro (twolip)
/e/OS-R V2.2 (EOL) heralds the end of /e/OS-(R)ed Velvet Cake. With /e/OS-T GSI new possibilities for degoogling will open up.