Hmm, I can't reproduce this.
The Metal Look&Feel doesn't seem to properly scale on HiDPI
screens but after adjusting the "Standard" font size", everything
is clearly readable.
Where does that "JetBrains" Font come from? Did you try a
different font?
sqlworkbench.sh already contains the only setting I know to
influence this
-Dawt.useSystemAAFontSettings=on
But even if I start it without that, I get clear fonts.
This is on an Ubuntu 22.04 VirtualBox VM
Alright, it turns out that the old build #128 works just fine.
Therefore, this topic becomes a bug report for the latest build #129.