Same here. It is my understanding it is a community built flatpak when developer does not have the resources (or won’t) offer one. Take for instance, Proton Mail Bridge. It is unverified, built by the Proton user community and I use it in some distros like Mint that includes updating the flatpaks with the system updates.
I do not use Snaps, but if a .deb is available, I usually do that.
I am not sure who decides what goes in the software centers on each distro, but I do know that TeamViewer used to be available in Mint and now it is gone from everywhere. Not sure why.
I have also added some to the repositories and later kept getting 404 errors. So that is not always an option.
Anydesk is still in the store but since they decided to start forcing 30-360 seconds “must watch” ads in the desktop app before you can use it, I uninstalled and switched to No Machine. And on MX Linux, it was in the repository.
So even if it is in the store, it’s not always FOSS. And those that are FOSS are often overused and just not an option for RDP. I tried Rustdesk and it worked once. After that, the servers were too overloaded. They ask that you host your own.
But Flathub is a simple store just for flatpaks. You can search for the app, and they give you the commands for install, remove & start from terminal. It is universal so that if you don’t have a “store” in your distro, you can install it easily.
Sheila