Decide what to do about the newly needed flathub-beta remote (for the beta fdo sdk extensions at the end of its cycle)
(Opening an issue here after a bit of discussion on IRC/Matrix, to get it sorted out for GNOME 41)
This issue is meant as a place to discuss this properly and find the solution we want here to keep the "Click to run" and avoid having all Rust projects (and Builder) needing to say to newcomers to install flathub-beta manually.
Because the GNOME master Sdk now depends on the beta freedesktop-sdk (until its stable release lands, and this will happen likely every year now if the plan is to depend on the beta fdo-sdk when available in the future), the different Sdk extensions (e.g. rust one and now LLVM one since it has been split from the main Platform runtime) need to come from the flathub-beta remote because that's where they are. Previously they were just picked up from the main flathub so we didn't have any problem with the "Click to run" as we already install the gnome-nightly and flathub remotes when starting up. But now that the flathub-beta remote is needed for the freedesktop-sdk extensions, we need to find a solution to ship it. The thing is, all refs on this remote have the same name/icon/app-id as their stable flathub counterpart, so it means that, especially if we ship it user-wide (and we need to), they will be potentially be shown and installed in GNOME Software when browsing apps and they will often cause a prompt to ask from which remote you want to have the app (or they will show duplicates when listing or searching for a specific app on the CLI). Technically it's already what's happening with our user-wide flathub remote we install, for the later, which is not great either.
So, some potential solutions are to set the no-enumerate flag on the flathub-beta remote we install. But then it doesn't allow us to list the available runtimes… @chergert proposed having a private flatpak installation for flathub-beta, so that it is only used by Builder (which would be the only one aware of it).
Related issues/MRs: #1458 (closed) !411 (merged)