I was using Chrome but suddenly it stopped working andI changed to Firefox. The only thing that I haven’t been able to do with it is what Ultra Surf did for me in Chrome. I use it to watch a TV show in Disney Plus that for some reason is not available where I live. How can I do this in Firefox? Thanks in advance.
So ultra surf is just a free VPN.
Free VPNs are notoriously bad, and usually sell your data.
The exception is Proton VPN free, which is a feed-in product to the paid service.
I would try that. Not sure if there is an extension though, you may have to use the Proton VPN client, which is better anyway.
Open Preferences > General > Network Settings…
Manual Proxy… for both HTTP and HTTPS Proxy for port enter the number 9666
Or to enable/disable quickly install Proxy SwitchyOmega addon… there are others too.