no more musesound

The same for me. It has reverted to MS basic sounds and no option to use MS sounds in playback setup

From the release announcement on 27 August 2024, see https://musescore.org/en/4.4 :
How to get MuseScore Studio 4.4 and Muse Drumline (new user)
Linux
The main download option will just give you MuseScore Studio. You’ll also need to download and install Muse Sounds Manager if you want to use Muse Sounds.
Please note that Muse Drumline is not yet available for Linux but we're working to address this as quickly as possible.
You can find additional builds on our GitHub Releases page, including a portable Windows EXE, as well as AppImages for 32-bit and 64-bit ARM Linux. (Muse Sounds Manager is not currently available for ARM Linux.)

How to get MuseScore Studio 4.4 and Muse Drumline (existing MuseScore Studio user)
To get the latest Muse Sounds, you’ll need to install the recently refreshed Muse Hub on Windows or macOS, or Muse Sounds Manager on Linux. You can download these from musehub.com. If you already have an old version of Muse Hub installed, it's best to uninstall it first before you install the new version. Please note that Muse Drumline is not yet available for Linux but we're working to address this as quickly as possible.

I have solved this by uninstalling musehub, reinstalling and then downloading afresh all of the orchestra sound fonts. Now it works perfectly. It's a pity MS didn't think to tell us that this would be necessary.