STM32G0 is definitely cheap and fun to play with. But... those OSC-pins scare the crap out of me. I would never run a XTAL off of an external header. XTALs are famously finicky, difficult, and have accuracy problems when specs differ by picofarads or picoHenries, and those headers will have more parasitics than that.
IMO, anyone building a development board (for themselves, or for others), should add on the 50-cent XTAL + calibration capacitors (probably just a few pennies) on board, where you can control the trace parasitics far better.
Any crystal anyone tries to add to this board is going to have a very hard time. Its one of those things that you need to get correct on the PCB board unfortunately, and you cannot route externally.