[gpm]

I managed to install calibre (6.11) on my headless server (Debian 11).
Everything works fine, except - in Firefox the server site looks strange. It shows the 'titlebar' (don't know how it's called) twice, one fixed on the top and one which scrolls with and on top of the contents. See attached pic.

This is only visible in FF, every other browser shows it correct.
The settings including 'server-custom-list-template.json' are the same as on my Raspberry which also runs on Debian 11 but calibre is v.5.12.
It is no critical issue but I would like to learn and know.