It's the first time I'm ordering the PCBs at jlcpcb.com, so I'm not entirely sure how this will go. Looking at the order status page, they have already shipped them, so I hope to have them here in a couple of days.

In the mean time, I found a mistake — of course! The SDB pin on the IS31FL3733 should be pulled up, while I am pulling it down. This is a third time I'm making this mistake, because on the schematic on the datasheet that pin is pulled down and connected to a microcontroller pin, so that the chip is disabled by default and can be enabled on demand. But in this case I want the chip to be always on, and I don't want to waste a pin for this. Fortunately, I can simply solder the resistor only by one of its pads, and use bodge wire to connect it to a nearby via.

I am also considering upping the display resolution to luxurious 16×16 by using an IS31FL3741 and four 8x8 matrices. That would of course require a redesign, and I don't have any IS31FL3741 at hand, so we will see. The 14×11 I have right now should be good enough, and four matrices instead of two would push the price a bit.