Until now I never had issues with Firefox.

But here in Germany the fanbase of ff ist larger. Maybe that’s why you don’t have problems with most of sites from Europe?!?

2 km bicycle ride to the train station, 25 minutes by train, 2 minutes walk to the office on the other side of the road.

Commuting in Germany.

I have a stream

Sounds like your nextcloud instance has a low limit for the upload file size. It has to be adjusted in the php settings of your nextcloud server. I set it to 1 GB and have no problem in uploading my videos using auto upload of the nextcloud app.