johano It's normal that when you click the Install button it tries to download the *.flatpakref file. The Install button doesn't know how to install things on your system. But if you scroll to the bottom of the page, you'll see that every package also lists straightforward command line instructions on how to install the packages.
It's doing the same thing you'd do (downloading the *.flatpakref and installing it), but in less steps. IMO it's the simplest way to do things 😉
Regarding the sudo thing, I would think once everything is installed and running, you end up with the exact same installation you would have w/o using sudo, i.e. you haven't given elevated privileges to your Zoom install. So there's no need to uninstall/reinstall it. My comment was more of a general warning to not systematically use sudo, even when you're installing things. If a command I run w/o sudo requires elevated privileges, it's an indication for me to pay close attention and to really understand what I'm doing/getting into 😉
Edit: Seems you found the instructions for the command by yourself 😆
