…have you tried GSI builds meanwhile ?
https://doc.e.foundation/support-topics/install-GSI
We also suggest you try to engage the XDA community to “stimulate” building:
https://forum.xda-developers.com/f/xiaomi-mi-cc9-mi-9-lite-roms-kernels-recoverie.9102/
Last but not least, consider to build (and, why not, maintain) yourself:
https://doc.e.foundation/support-topics/build-e
(Re)sources:
https://github.com/SDM710-Development/android_device_xiaomi_pyxis
https://github.com/SDM710-Development/android_kernel_xiaomi_sdm710
Hope that inspires !