Just loaded the latest Vember Surge version (Latest Release: 1.8.0 (2021-01-17 )) in the latest Renoise version (3.3.1) and the glitchy GUI (together with crashes) is back. This was fixed, but they seem to change / break something.
This is on Ubuntustudio 20.04 with XFCE.
I happened to blow through with a bug of my own (turns out it was a distro issue). You’re using a nightly build of Surge.
I’m using the current 1.7.1 release from the .deb on Surge’s front page, and it’s working fine.
current is 1.8, released yesterday 
Oops, scratch that. I was apparently using 1.8 when I posted that, as well. Either way, I guess I can report it works fine in Mint 20.1, which has the same Ubuntu 20.04 base.
Sometimes it worked, sometimes it was crahsing, sometimes just glitchy. Will check again the next days…