Well as @Zanna had said, there never existed such links natively, but I was using this fine userscript
SE Modifications
which is apparently broken (at least in my installation) right now.
Before switching to tampermonkey I was looking forn an easy way to transfer the userscripts and stumbled over Userscript works in Tampermonkey on Chrome but not in Greasemonkey on Firefox (Stack Overflow), where I found
Add before // ==/UserScript== on a new line:
// @grant GM_addStyle
Thats all that was needed (strange how it worked until now...)