Not sure this has been said here before, but it’s well established that working around this bug involves changing the folder you store your music in to “Guess Access Read/Write” or “Read Only”. And if you reboot the machine, then Roon Core forgets the local files requiring you to rest the Guest Access privs. What I didn’t realize until now is that the privilege setting for Guest Access doesn’t really matter. Just changing it to something else is enough for Roon Core to rediscover the library.
For example, my QNAP TVS-h1688x (Quts Hero 5.0.0.1856) was originally set up as Guest Access Read Only on my music shared folder so Roon could see it. Then I had to reboot the machine and Roon Core forgot about the music share. But this time I changed the Guest Access privileges to “Deny” and lo and behold, Roon rediscovers the music shared folder. So it doesn’t matter what you change the Guest Access privs to, the point it that it has to be changed from something to something else…anything else. Weird.