(Hi! It is clear that Linux is not supported, but I thought about reporting this problem since all the rest of Scaler2 VST3 works wonderfully on Bitwig with Ubuntu + Wine + Yabridge)
It is very hard to get the floating menus to show up. Clicking the left and right arrows always works, which at least allows to chose options, but in the menus with dozens of options this is tedious. Another Scaler2 user is running it with Bitwig+Linux and cannot reproduce this problem with the menus.
Here is what I have tried:
With the default window size, the menus wouldn’t open. The “SELECT…” message at the bottom right of the window could be seen in most clicks.
Then I thought about making the window bigger. This made the instruments menu work properly and (apparently) reliably.
Now, with the Perform, Songs, and Artists menus it’s a hit and miss. I haven’t found the pattern. If I click on, say, Artists every second and (just for fun) clicking every time a different letter of the label “ARTISTS”, then it is very likely that the window will open within 2-10 clicks.
Other buttons like Scales, Suggest, etc, work perfectly. It’s something specific about these menus.
Anyway, I hope this report from an unsupported platform helps somehow. 
Thank you for this excellent product!