I can't seem to access the F3 Debug screen, and I don't see anything about the mod intentionally disabling it. I haven't been able to find anyone else with the issue, but it's rare for people to game on Debian, so I'm unsurprised.

Minecraft 1.14.4 with Optifine and JEI. Forge 28.2.0.
Playing on Debian 10 x86_64.