JetBrains Mono: A free and open-source typeface for developers 7 years ago
Ok I tried out the font. It’s actually more difficult to read than Fira Code. YMMV.
To me, everything is too thick and crammed together compared to Fira. It just feels like the font wasn't designed with enough letter spacing. I think you can manually control this in IntelliJ products, but the default spacing seems too crammed.