Please test with the latest LE10 nightly build from here
https://test.libreelec.tv/10.0/RPi/RPi4/
ISTR 10.0.2 had some (composite) bugs that are fixed now.
Editing distroconfig.txt isn't ideal (as it will be replaced on updates) but should work - better keep a copy of it when you got it working.
I've thought about better solutions like having a separate distroconfig-composite.txt but while working on that composite configuration in RPi kernel/devicetree changed again and I decided to wait a bit until things had settled.
so long,
Hias