emoji have randomly stopped displaying in swaywm after a system upgrade i did back in December. i thought it might just be an intermittent bug but this has been going on for a while now and i haven't been able to find any solutions online. any ideas?

Do you still have the generation from December around?

If you <generation>/bin/switch-to-configuration test it, do emojis work again?

If so, find out which revision of Nixpkgs you used back then and do a git bisect with it as the good rev and the current nixos-unstable as the bad rev. Use --first-parent to skip staging commits.
Test each revision with nixos-rebuild test -I nixpkgs=/your/nixpkgs/checkout. After you've gone through the process, you'll end up with to the commit that broke emojis and you can open an issue in Nixpkgs with that information. Perhaps you can even fix it.