Oh - I was gonna look up last night (if trellis supports variable brightness)
(reading the datasheets, etc.) Looks like the HT16K33 chip on the Trellis can dim the entire display (or maybe rows at a time) but not individual leds.
So - maybe this is good timing. I’m in the midst of redesigning the Trellis board for my own needs, so I could look into using the TLC59116 chip instead. There seem to be a number of github repos with TLC59116/arduino code, so one would hope it’s just a matter of getting the i2c commands right and interpreting the serialosc info
EDIT - I think the TLC59116 is missing “keyscan” which is needed to get button presses. Investigating other chip possibilities.