I tried @popov's steps for getting Addons to work on a Pi 3B+ running the new 0.5b beta. I was able to see the addons menu and install the Rune UI enhancements just as @popov said. Thanks very much for your efforts to get the addons fixed.
Now I could see the UI enhancements fine, and play network files from a synology diskstation. However, I now had another problem: When I tried to update a folder in the library, all I got was a spinning circle, and I could no longer see anything in that folder. I could still play music from other folders, provided I didn't try to update a root or other higher level folder. But any attempt to update any folder resulted in the spinning circle and the loss of the ability to see anything in that folder again. The files were still visible in /mnt/MPD/NAS/mynetworkshare.
I don't know how or why these minor changes to one file could possibly affect the ability to update a network folder, so I have to think it is the UI Enhancements that are somehow causing this. I could update folders before I installed the enhancements on the same image, and after uninstalling the UI enhancements I could update folders with no problem. But when I reinstalled the UI enhancements yet again, I couldn't update any folders--I just got the spinning circle.
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