What distro are you on? Some don't install all available KIO workers and you'll have to install them yourself.
Is this something that is likely to improve going forward?
Like any FLOSS project, things tend to happen when programmers decide to solve a problem for themselves. If you don't the the skills to do this, you could always bring it up on the KDE forum under the "brainstorming" category, submit a feature request on the KDE bug tracker, or sponsor a developer to perform the work.
Seconding Navidrome. I stream from my Navidrome server to my phone, and then via DLNA from my phone to my HiFiBerry / stereo system. It's very nice.
Maybe not - I've heard those things can get really hot inside like a greenhouse
I thought you could only select from a pre-defined list of addons in Firefox mobile?
I find the yunohost mailserver pretty good ootb
Tried updating your bios?
Before the last word.
What’s a beginner to do
Well that's just it; Endeavour is not a beginner distro. It's not designed to be. Endeavour is Arch with a graphical installer and some modest quality of life improvements for users who are otherwise willing to trawl through the Arch wiki for answers. The welcome app really just seems to be there so that you don't have to memorize all the commands or set up aliases, etc, if you don't want to.
So when you ask "am I supposed to X," the answer is that there really isn't a set-in-stone workflow to accomplish anything on EOS or Arch; what you're supposed to do is read the manual, so to speak, and decide for yourself how you want to go about things.
Unlike some other Arch based distros like BlendOS and Manjaro, Endeavour is still very much a DIY distro.
I would try searching "kio" in your package manager.