This developer specializes in Korg emulations. While they focus more on the analog era (like the Poly-800), their plugins provide that vintage Korg character for free.
Many sound designers offer free "M1 Tribute" packs containing multi-sampled versions of the Piano 16' and Organ 2 patches. korg m1 plugin free
For those seeking the specific "tines" and electric piano sounds found in M1 patches. Using Free Soundfonts and Sample Packs This developer specializes in Korg emulations
Specifically grainy digital reverb and chorus. korg m1 plugin free