While looking at the Teensy, I noticed basic support for the CS42448 (slightly more advanced user HW designs can be found by searching the web). Since I don’t feel like building my own PCBs, I came across a “6 in 8 out CS42448 multi-channel decoding electronic 4 frequency divider board” on Aliexpress, but I have not found time to experiment with it yet. Anyway, compared to Paul’s design it does not implement the CAT811T reset chip (whose purpose remains unknown to me) nor the additional PCM1808 DAC needed to upgrade the CS42448 from 6in/8out to the full 8in/8out. And it is equipped just with the tiny 3.5mm jacks (one for each pair of channels as unbalanced I/O only).