So it doesn't sound like an isolated incident - Apple should actually react to that

Hi, The same to me. I upgraded my MacBook Pro to OS Big Sur yesterday. Since then I can no longer access a certain website on Safari - the browser loads and loads and loads ...... If I call up the same website on Firefox (it is not my standard browser) without problems. There are no problems on my other iOS devices either. Likewise, all (!) other websites can be opened on Safari as usual and without problems. I have already contacted the owner of the website concerned (service provider). He confirmed to me that in-house tests on Big Sur were successful. Do you know the problem or do you have a solution?