I switched to Adwaita-dark gtk theme and found I coundn't see the icons on the buttons very well when using yt-dlg, so I made a quick fix for anyone who is interested.
The black icons to me only look good on white or light background colours, so making them bright white stood out more on darker backgrounds for me and there's probably a few others out there that like the darker themes and use this program. After updating or (re)installing yt-dlg you will have to reinstall these pixmaps, instructions provided within archive.