Like many, and before 2.65, my system would become borderline unusable because of slowness - albums/playlists taking forever to load, and 5 second or more delays between tracks. I got so frustrated that I followed another thread on this forum and reset my database. I then re-scanned my local library, logged back in to TIDAL, and I was mostly back in business. Lost all favorites, hidden albums, etc., but my system ran like it should.
But pre-2.65, the problems returned, even with the new database. But I kept using the new one anyhow.
Now, with 2.65, the new database works great and continues to do so. For an experiment, I re-loaded the old database, now running under 2.65. After a number of minutes, the UI appeared and I played music; it was like turning back the clock. The playlist took several seconds to load, and there was at least a 3 - 5 second delay between tracks.
I went back to my old/new database and all is good. FYI I have a smaller library, about 40,000 tracks. Everything is on Ethernet, and my Core is on a Roon-spec NUC.
The obvious answer: My original database was corrupted in some way, that caused either version, pre- or post-2.65, to perform terribly. 2.65 fixed whatever caused even a fresh database to slow down, apparently, and at least for me.
YMMV - but I thought this might be helpful to some.
Note that after restoring a backup, roon needs time to sort metadata, that is what the Settings > Library > Background work maintenance plan is for. Before this is fully sorted, UI might be sluggish.
Have experienced similar situations with both the SSD storage location for the database being corrupted, and database file structure itself. A fresh install install and backup restore helped in both cases.
Irrespective of technical problems, there seems to be something that is making roon struggle more with a particular library structure than with a different one. Anecdotally, I have identified a few aspects which were seemingly slowed down things with my previous machine over proportionally, like lots of boxsets/albums with enormous amounts of credits, lots of unidentified albums, tons of merged artists and compositions, lots of DSD files, and some people report the same about overly complex local folder structure. In these cases, removing just the right few thousand tracks from a library of nearly 100,000, made roon significantly more reactive.