On 25/06/2020 04:59, Valmor de Almeida wrote:
> Hello,
> Does anyone know how to fix Thunderbird UI fonts on a HiDPI
> Gentoo/OpenBox system with no desktop?
> A similar problem exists with Firefox but it can be fixed using a CSS
> file (userChrome.css). However I can't get Thunderbird to work using a
> similar fix. The UI fonts are so small that the app is useless.
> Thanks,
> --
> Valmor
> 

Do you have an ~/.Xresources file? It can have something like:

Xft.dpi: 144

Which is also passed to Xorg for me: -dpi 144 (Plasma does this by
modifying SDDM service file(s) to systemd).