I’ve made a usercss style for Stylus. (It might work with other style managers as well, but I haven’t tested yet.)
If you have Stylus installed, you can install the style by going clicking on “install directly with Stylus” on the main page of its GitLab repo, or just clicking here. (Alternatively, there’s also a mirror on GitHub.)
It’s based on another userstyle I made a while ago for Manjaro Linux Forums and I realised that it’s for the most part compatible with FCC’s forum (since they both use Discourse), so I decided to share it here. It’s not perfect, but my intention is to polish it until it gives a consistent, pleasant dark theme experience.
If you have a suggestion, let me know here or create an issue on GitLab. Pull requests are also welcome.
Edit: updated repo and raw link and added screenshots.
Edit 2: added link to GitHub mirror.