Azania
commented
3 years ago This is due to your version of gnome-settings-daemon. Since 3.32 you can no longer get brightness or max brightness from gsd-backlight-helper. You can only set with it and you have to add the device as well. So the current version will only work when you run gnome-settings-daemon below 3.32. Since it can't read a max brightness there is no value for max value of the slider and thus the slider won't show.
For the ebuild of budgie software I made for gentoo I wanted this applet as well so I actually modified the source in order to get it working. It reads /sys/class/backlight/ to get the first device it finds and shows the slider for that one. You can use that for the time being if you patch the source from project till the owner fixes it in a more clean way. Its not entirely clean as it skips anymore it finds but it does work nicely like it should be when you have only 1 backlight device.
Anyway the patch for now is here: https://gitlab.com/SarahMia/sarahmiaoverlay/-/blob/master/gnome-extra/budgie-brightness-control-applet/files/fix_applet_massively.patch
Simple way for multiple backlight devices imho is to add a slider for every single one and add label in front of it of which one it is. Otherwise in settings select a device. I suppose but that would take more effort I suppose. Or maybe a combination of both with checkmarks in settings for which ones you want to show.
Anyway hope it helps.
I've used this applet before without any issue on the same machine...But this time I couldn't control the brightness since there's no sliders, signs(+/-) doesn't work either
I couldn't reinstall since idk how to uninstall first, I just tried re-installing without uninstalling, yet found no luck Im using Solus Budgie
tnx