Regarding contacts, you can always fill up the form for support on our website and you should get a response email. As Wayne already answered to you in email, chats are saved and if anyone is available you will get an answer right away (which is not always) and if not, your messages are saved and you will get an email for your response (which i was told you did get a response). Our support chats are available in matrix and telegram (bridged rooms, messages appear in both) and if you do not want a commercial service you can ask your questions in this forum and get an answer like all other users. We do not have a discord channel/server, at least not yet.

All applications in Flathub and Debian repositories you can install and run, now how good it will be on a small screen is a different question. Most GNOME applications are usable on mobile devices since they are adaptive to their environment. Pure QT or pure GTK based applications depend on the developer if they make it mobile friendly. QT applications built for plasma fit nicely on the screen. Again, you can "run" everything built for ARM64, meaning they will show a UI, but that UI might not be compatible and usable on a phone sized screen

Applications from flathub are updated as developers push updates, we are not involved. Applications from Debian get updated once every month since we freeze the repository for fixes and stability at the end of each release and update it for the next.

If you have an application from snap store you can install those and you will get updates from the snap store. if you have an application that is a standalone binary that you have downloaded yourself then you are in charge of updating it. For apps we develop, we push updates to production on a monthly basis and you get the updates either through the software store or apt by manually running apt update and upgrade.