There's also Route 53 in AWS. Might be handy if you already have an account there. You also get free SSL as long as it's hosted in AWS.

The multi-account container add-in just keeps cookies and therefore sessions separate. I use it so I can log into systems like AWS/Azure using multiple accounts without having to resort to multiple browsers and/or incognito mode. Things like saved passwords are available across all containers. Useful recently where I could setup a new container for my daughters Teams classes without having to log out of my own Teams session. FYI. You can use the History --> Recently closed windows menu to get back lost windows.

Might be worth trying the "multi-Account containers" add-in for firefox.