About 3 weeks after transmitting the KiCad gerber files 3 PCBs arrived from the USA. To my surprise the finish is ENIG (gold) not HASL or similar, which looks great. This makes the price of my small prototyping batch even more surprising!
The soldering mask of the KiCad TSSOP footprint, and very accurate rendering, made soldering the µC easier than thought, certainly easier than any cheap "TSSOP20 DIL adapter PCB" I soldered so far.
Of course I made a mistake with the PCB, but it's a minor one: the drills for the CR2032 battery holder are a bit too small. Half a minute with a nailfile made the pins fit in. No problem, but I'll update the PCBs. Otherwise the components all sit at the right spot.
In the meantime, the nRF24 code has been refactored and made ready for using STM8L051 instead of STM8S103 (or for any other STM8 eForth target). Hopefully I'll get to implementing the Ping application soon :-)