Apparently GPU hardware acceleration sometimes gets blocked by Linux. I just added a flag that will detect this and display the following message:
“PERFORMANCE ALERT: This game is running with slow CPU rendering (no GPU acceleration) and will experience severe lag. To fix this, enable 'Hardware Acceleration' in your browser settings, or try switching to another browser (like Chrome) or a different device.”
I just read your other comment too. Glad to hear it is working without issue!