Thanks for your report.

I have added this issue to the tracker:
Issue 2392 – Command md5sums is incorrectly used to calculate MD5 checksum instead of md5sum

Dear WinSCP Community,

I'm using WinSCP 6.5.3 on Windows 10 with default settings. When calculating checksums via Properties > Checksum, the embedded command uses md5sums, which fails on Linux hosts with the error:

Command 'md5sums "filename"'
failed with return code 127 and error message:
-bash: line 9: md5sums: command not found

This happens because most Linux distributions provide md5sum instead of md5sums. I can create a custom command using md5sum, which works fine, but it doesn't integrate with the Properties > Checksum feature.

Is there a way to configure or override the embedded md5sums command to use md5sum in the Properties > Checksum menu? Alternatively, could this be considered as a feature request to allow customization of the checksum command or support for md5sum by default?

Thank you for your help!