did you tried an recent Nightly LE version, Kernel 5.7?
It is very likely that the 5.1 Kernel has problems with that stick (maybe DVB related, maybe usb ...), everything else you tried (tvh board matrix) has an much older Kernel or the Ubuntu versions carrying massive kernel patches.
I just tried that, but this did not seem to improve the situation:
|Start time||Hardware||OS||Kernel||TV tuner||DVB Module||PVR||
||Poor signal count (s)||UCB (uncorrected blocks)||
First UCB at (s)
|06/08/20 17:52||HTPC||LibreELEC-Generic.x86_64-9.80-nightly-20200804-a26fe97||5.7.6||AVerMedia AVerTV Volar hd2||dvb_usb_af9035 5.7.6||TVHeadend||yes||50%||pink+ blue||2500||93||58448||1208|