I can confirm that the wnienhaus/languagegame recipe above just worked for me (OpenWRT 19.07.04 on GL.iNet GL-B1300, iOS 14.2, iPhone SE 2016). Phew!
As an 'intermediate-level' user, I did not fancy my chances following some of the expert solutions posted, involving recompiling Linux kernel etc. - though I see why they are superior if one is able to execute. Whereas the wnienhaus/languagegame recipe is much easier to follow!
Hopefully the next OpenWRT supported build release will include a full fix (done the expert way, of course!), to complement the excellent work of luochongjun, who has compiled a full new set of patched GL.iNet snapshots (which are built on OpenWRT, of course).
I believe Apple broke this functionality deliberately for the Linux/OpenWRT community - their inadequate response since speaking for itself - so it is great the community has fixed it so quickly, thereby sticking two fingers up to the money men!