mrtn
Dagobah Resident
@Maat, you said you tried safe-mode, but can also try
Firefox Menu (top right ☰ icon ) > Help > Restart with Add-ons Disabled...
If that helps you can quit Firefox and start it again normally, then
Firefox Menu > Add-ons > Extensions
There you can disable individual Add-ons to see wich blocks it, or better disable all and reenable one at a time. You might have to restart Firefox depending on the Add-on.
Firefox Menu (top right ☰ icon ) > Help > Restart with Add-ons Disabled...
If that helps you can quit Firefox and start it again normally, then
Firefox Menu > Add-ons > Extensions
There you can disable individual Add-ons to see wich blocks it, or better disable all and reenable one at a time. You might have to restart Firefox depending on the Add-on.