I am running cygwin virtualbox running a WinDev2206Eval "appliance" (.ova
from microsoft).  Everything else I've tested so far in cygwin runs as
expected except scp when the <source> file path is an absolute path, e.g.
/tmp/foo.  Scp <source> references to that file using a relative path, e.g.
../../tmp/foo, work fine.  For example:

$ ls > /tmp/foo   # create a /tmp/file
$ ls -l /tmp/foo
$ scp /tmp/foo bcserver:foobar  # fails with /tmp/foo "file not found"
$ pwd    # (CWD is /Users/dmk)
$ scp ../../tmp/foo bcserver:foobar   # this works
$ cd /tmp
$ scp foo bcserver:foobar   # this also works

Please see the attached (script) log file scp.log for the actual results
using these commands.
See also the attached cygcheck.out file.

Note that:

  1 -  absolute paths work OK for an scp <destination> pathname

  2 - the "scp /tmp/foo bcserver:foobar" command works OK in win11's
PowerShell

  3 - the scp target host (bcserver) is a FreeBSD 12 OS running in a
TrueNAS "jail".