Is there a "Dark" mode theme for steam gifts

Not natively, but there are scripts to do the job. I use this one
https://www.steamgifts.com/discussion/62TRf/steamgifties-blackblue-update-november-11th-v285

Yep.
Install this:
https://github.com/rafaelgssa/esgst/releases

I'm using SteamGifts v2 Dark , it's also built into the ESGST addon.

UserStyle: https://www.steamgifts.com/discussion/iO230/userstyle-sgv2-dark-159

Add-Ons: https://www.steamgifts.com/discussion/Zevqn/sg-add-ons-registry-list-of-all-scripts-for-sg-update-30-aug

If you want more styles

https://userstyles.org/styles/browse/steamgifts

I wish cg added a dark mode theme, using SG on mobile is way too bright for my eyes at night. :/

Coolio good to know that there are solutions, now to dig through these options. Thanks.

Darkreader.org -- apply dark mode to everything

wish the guy who runs this web site would just add a dark mode switch.
i use firefox addon