The day has come, I finally ordered my first PCBs today! 10 boards were ordered from Elecrow, now I can't wait to have them arrive. Fingers crossed there aren't too many serious goofs left in the design. In the meantime its time to order all the parts I'm still missing, which is quite a long list actually.
While the boards are in manufacturing, I hope to find the time to get the firmware in a usable state, with MQTT working and all. The IRQ issues I was having yesterday are fixed by now, bit of a stupid mistake. I had two scopes hooked up and was scratching my had why on earth the ISR isn't being called, just to find it's a falling edge instead of the rising edge I have to trigger on. What an obvious mistake that was, but you never stop learning :-)