Hello - so I just moved to my M1 Macbook Pro from my 2019 model. There was one HDD which was not picking up on M1 while it works totally fine on 2019. I tried on other devices also. No Problem at all. So then I looked at the format. The one which was not picking up on M1 was formatted at NTFS, while the ones having no trouble were on MAC OS Extended (Journaled). I formatted my problem HDD as MAC OS Extended (Journaled) now and its working! Worth a try - Best of luck!