Customise thunderbird 78 looks – Super User

Gday gents.

I’ve got a thunderbird 78.7.1 (64bit) install here on win10.
Trying to change the looks a bit, because even though I like the light interface, the header row in the list is indiscernible from the rest.

However, it seems that all the themes are incompatible with this version, in fact most mods are.

I’ve looked at trying to use the userchrome.css method mentioned somewhere, but only god knows what the styles are, and firebug is also incompatible so I’ve no idea how to find the classes/ids of the elements in play.

Anyone can recommend any way out of this? (apart from switching email clients – I can figure that one out myself)

Many thanks