Having the same issue with my 2018 iPad Pro 11 inch. Safari is unusable.

I too had to re-install from scratch between beta 2 and beta 3. Now same thing happening between beta 4 and 5. Always fails after update is downloaded then says failure occurred check your internet provider. There is absolutely nothing wrong with my internet provider. I'm done with the beta for macOS 11. I will just wait for the official release, too bad though I found it to be a really nice update on my 2019 27' iMac.