Thank you for this project.
I have found an issue with the colour palette: when I change it in the general settings, the theme apply correcty (and is saved in local storage), but on a new page load (after a refresh) the data-theme attribute is missing from the html tag.
Deployed locally with docker.
Tested on Firefox and Chromium.
No issue on the live demo.
Thanks! Somehow I didn't see your issue earlier. Fixing it