0.21 branch (0.21.0....0.21.4) is based on 0.21.0 (released in 2022) and contains bugfixes and stability improvements (like move all allocations from non-initialized malloc to zero-filled calloc).
No new cameras, no new RAW formats, stability-only changes.
Snapshots contains new cameras/new raw formats support, but may be not as stable as 0.21.xx
0.21 branch (0.21.0....0.21.4) is based on 0.21.0 (released in 2022) and contains bugfixes and stability improvements (like move all allocations from non-initialized malloc to zero-filled calloc).
No new cameras, no new RAW formats, stability-only changes.
Snapshots contains new cameras/new raw formats support, but may be not as stable as 0.21.xx
This is explained in details in the update policy section on this site frontpage: https://www.libraw.org/#updatepolicy