Quite perfect IMHO! installed in a breeze on my N910C.
Edit: I installed from TWRP 3.3.1-0, the latter system was lineage_treltexx-userdebug_10_QQ3A200805001.
On TRWP I performed a factory reset, then wiped Dalvik, Data, Cache and rebooted to reecovery. Then installed lineage-17.1-20210304-UNOFFICIAL-treltexx.zip.
No more black screen during calls, neither on calling nor on receiving. I've been waiting this fix more than one year long! No word can say how grateful I am! You succeeded where most developers fail until today, I also have an J530F, also running LOS 17.1 that yet needs this fix, so I came to think that it were a LOS 17.1 bug.
Camera is OK, also tried Footej #2.
One billion thanks again for your VERY GOOD WORK!