After reading all of the messages around this situation I am still confused as to how I would compile a proper firmware now. Is it currently not possible to compile for a newer kernel and I would have to revert back to 4.19?
It sounds to me that the initial flashing is more problematic, but the subsequent OpenWrt sysupgrades might be easier.
Yep, that's also my understanding.
The problem now is to fully understand how to get past the initial flashing period.
I noticed that the uboot on this devices has a limitation of 16MB, but back then I used to do a stock compile of OpenWRT, flash that since it's <16MB, then compile OpenWRT with the packages I want and do a sysupgrade.
Now I can't seem to figure out how to get to a stage to even flash a "clean" build.