Well, the title about covers it! I have exactly one program that doesn’t follow the KDE theme, Alacritty, and they’re a little, hm, hostile towards people that ask anything that might be done by the display manager.
So, I’ve searched high and low, and haven’t found a single person who’s managed to do this. It’s all “change your theme or whatever”, but, I’m apparently lame, because I really like Debian Breeze, and I don’t want to switch to a dark theme. Sooo…anyone have some ideas? 
You’re my last hope!