I don't even believe that no one didn't comment this PR magento#31618 during 2 year. Do you know that styles sourcemaps are broken since updating this package in package.json.
each time it has to be fixed for a new project.
grunt-contrib-less 1.4.1:

grunt-contrib-less ~2.1.0:

you ask for self-checking, tests running, screenshots, but don't check the first development steps when you update something. that's weird.

steps to reproduce:

1. setup a new theme
2. prepare Grunt files
3. run npm install
4. run grunt clean:theme && exec:theme && less:theme
5. see that sourcemaps not generated even if you disable static sign, cache, browser cache, etc.
6. restore the package version to 1.4.1 from ~2.1.0
7. run npm i
8. repeat the 4th step
9. see sourcemaps in the browser's devtools.

video example that includes the fix (use subtitles) with timecode:
https://youtu.be/NEKvPRTW9mM?si=2f_ZXV-WNR8IyN9N&t=699

that's even funny that in M2.4.7 beta this package is update to ~3.0.0
magento@203f415

but it couldn't be compiled with error:

Running "less:demo" (less) task
>> pub/static/frontend/Vaimo/demo/en_US/css/source/_reset.less: [L7:C4] Error evaluating function `unit`: the first argument to unit must be a number. Have you forgotten parenthesis?
Warning: Error compiling pub/static/frontend/Vaimo/demo/en_US/css/styles-m.less Use --force to continue.

Aborted due to warnings.