I always had DeepDark. I'm checking all themes for a satisfactory replacement. Looking through "Complete Themes by Name" and every theme I hover over says "this add-on is not compatible with your version of Thunderbird". EVERY SINGLE THEME. I'm not talking a few, this is over 100 themes. Thanks for being so full of crap re how customer focussed you purport to be. And Don't answer me by saying I can use default "Dark" theme, that's not the point. I should be able to choose any theme for the one I want, just like previous versions of Thunderbird. That's my point. Don't give me a spurious answer. Fix it, tell me what I'm doing wrong, or apologise and admit you guys are hypocrites and no better than those competitors whom you criticise.