Yeah I agree with you there, far to little good resources on Power Query M, at least that I’m aware of.
I’ve listed some below altough these are pretty well known but maybe others can add to this list…
YouTube
Mike excelisfun Girvin Power Query (Get & Transform) Video Playlist
Oz de Solei Get and Transform (Power Query)
Blogs
Chris Webb https://blog.crossjoin.co.uk/
Imke Feldmann https://www.thebiccountant.com/
Ken Puls https://www.excelguru.ca/blog/
Gil Raviv https://datachant.com/