[note: i know nothing about GPS, don't ask me directly -- here are my notes:]

M10 full-support merged Aug 11 into "4.5-zulu". (Exists in 4.5-RC1 and later.)
- https://github.com/betaflight/betaflight/pull/12799
- Use [nightly Configurator 10.10 ](https://github.com/betaflight/betaflight-configurator-nightlies/releases)

iFlight blog How-to:
- https://iflight-rc.eu/blogs/news/m10-gps-3d-fix-enhancement

Bardwell on the subject:
- https://youtu.be/ZrZbRzqQNVo
- https://youtu.be/eBzQLVYOy9Y
- https://youtu.be/5fBDqeAoqvI - most technical here.
- https://youtu.be/w5QkoGJIW2w