Follow system theme

[xplosionmind]

Use a CSS property to detect the system theme and set the web interface theme accordingly. Allow the user to choose a default dark and a default light theme.

See GitHub themes as a reference:

[MicroDroid]

I kinda wanna fix this but I am busy with finals :(

[julianfairfax]

I would also like this feature!

[munkacsimark]

In v4 there are six themes. I think Proton should be the default light and Carbon the default dark.

[julianfairfax]

I think that should be the user choice because I would prefer Snow as the default light theme