1Password has some strange issues logging in on a specific website

I want to login at my hosting provider at hostnet.nl. The first time I discovered the issue after the Microsoft Edge update about a week ago. After filling my login credentials, the login hangs on the dashboard page (it keeps loading). It does not fully load, and also I see a big red bar on top of the page telling me the page does not exist anymore. When I click on a link, I am redirected to the login page again. Other chromium browsers (and also Firefox) did not have this problem. Until yesterday when my Chrome and Brave got their chromium updates, too, and the same issue emerged in those browsers, too. Now the issue is present with all chromium browsers on every platform and os (windows, macos, linux, ios). It doesn’t make any difference when using these browsers with or without extensions, in private mode, to reinstall them, etc.
I can login on the chromium browsers on that site with eg. Proton Pass. Or by using the old school copy-paste of the login credentials. And all dev-beta-canary versions of these browsers, and also the 1Password Nightly extension have the same issues. Apparently this bug has not been reported anywhere yet.