I guess I mistakenly assumed all modern Arduinos have built in EEPROM. Is there no built-in NVR options in the XIAO? That would be really unfortunate.

Seems the datasheet shows some sort of EEPROM emulation features. Are these not implemented in the XIAO?

There should be, but I haven’t seen it yet.

I haven’t tried it yet, but it seems there is no EEPROM, but EEPROM emulation in flash. In the arduino IDE package for the XIAO, there is an example in there using flash NV storage. Unfortunately it gets cleared every time you upload new code, but it will keep data between power cycles.

They are available in the IDE Arduino library manager.

Also available in the IDE Arduino library manager