I use a Mac Mini late 2012 with Mac OS Mojave 10.14.6, running AS 1.8.1.
I have observed this for a long time, and as suggested elsewhere, I managed to have my local albums show after fiddling with the filter bit.
I confess I do not find this workaround satisfactory.
This only happens when Audirvana Studio is playing music.
If playing is terminated (not just stopped) by clicking on the padlock, the local albums show back again, but after selecting either local artists or local tracks, and then local albums.
In contrast, the display of local artists or local tracks is not affected while music is being played.
To put it mildly, this is annoying, and surely warrants a fix.