A little confused.
Cinnamon Nemo can already open anything with Atom by using Open With.

There is no need to make a nemo.action to do such a thing. Also I didn't see any uninstall .sh, nor any not-cinnamon-desktop has this.

The piece of code introduced with this commit seems to cause an error, when launching atom from command line:

$ atom test.txt
cp: cannot stat 'resources/linux/desktopenviroment/cinnamon/atom.nemo_action': No such file or directory

System is linux mint 20.3 cinnamon, atom installation via apt. Fresh install.

As far as I can diagnose it, the atom script (usually located at /usr/bin/atom) cannot locate the atom.nemo_action file when not compiling from source. I would suggest to comment/disable this bit of code in the startup for now.

As nicely pointed out by @catscarlet, Nemo can already open anything with atom using Open With

Good evening,

I just opened issue #25294 on this issue.
This persistent error message is annoying.

Best regards.