You can just use MKVToolNix to add the second track to the MKV file after rendering, it’s still another step but doesn’t require re-encoding.
If you’re just trying to multiplex tracks and not actually edit the video, I’d recommend doing it entirely with MKVToolNix and skipping Kdenlive for this use. I’ve done this previously to combine a subbed video and a dubbed one into one file, you can offset or stretch the audio if needed as well.
Why “foreign” bad actors? Reddit is a US company and has “former” CIA in high-up positions. The site is heavily astroturfed by US military and intelligence. The prevailing opinions seen on the site are extremely pro-NATO and pro-“Israel”. If foreign actors are trying to influence the site, they’re in the extreme minority.
The site is of course also heavily botted to fake engagement, similar to how twitter is, but i think a lot of the unpleasant people on there are real. The site caters to their hostile, antisocial behavior.