I don't use the HD Austria addon myself (don't have a subscription for that) but I strongly suspect it's an issue with that specific addon, so best to report it on it's issue tracker.
You can safely ignore the inputstreamhelper messages in the log (they are false-positives, the checks it does don't work on LE) and the inputstream messages may be a result of issues of the HD Austria addon.
We have an inputstream.adaptive update to 20.3.14 in the queue (new addon should be build and available in the next days), you could wait for that and retest once you got the update but the changelog doesn't look like it might help (it seems to fix subtitle stream issues).
It could be due to some bug in inputstream.adaptive but only the HD Austria addon devs are able to narrow it down as we're not familiar with that addon - hence best report it to them and let them figure out what's wrong.
so long,
Hias