(moving the LED brightness discussion here)
My SQ-64 just arrived. I pulled it out of the box and plugged it into the unpowered USB-A hub hanging off my Mac Studio. I could not see the LEDs in direct bright sunlight (the OLED screen was readable though). Once I closed my shades, the LEDs were relatively easy to read. I put in a pattern and jammed a bit with Ableton’s Operator. Easy to use step sequencer with solid basic functionality!
After playing with Ableton, I powered the SQ-64 down and connected the USB cable to one of my Anker multiport power bricks. All of the LEDs were suddenly much brighter, making it difficult to distinguish between steps that are on and those that are off. Previously the “off” LEDs were too dim to see. Fortunately, you can hit the Global button and then the key at the intersection of B row and Polyrhythm column and change USB power from 2A to 500ma. Now the sequencer is easy to use.
This may become slightly bothersome as fall rolls into winter and I want to keep the windows open for as much sun+heat as possible (I’m told Chicago’s winters aren’t quite as warm as SF’s), but should be tolerable.
Overall, I’m already satisfied that my $200 was well spent. TRS ↔ DIN adapters should arrive Friday and then I can sequence the Virus with the SQ-64. Should be fun!
Edit: I don’t have any TRS ↔ DIN adapters, but I do have 3.5mm to 1/4" cables, so I plugged the Syntrx into the SQ64. It just worked, and now I can choose between the Keystep 37 and SQ64 for Syntrx control duties. 
I’m sure I’ll meet the bugs soon enough, but I have zero buyer’s remorse so far.
Next step is to decide upon my preferred way to connect to the Lyra-Ornament Adapter’s posts, order one of those, and build a cable harness to allow the SQ64’s percussion sequencer to make suggestions to the Lyra.