LibreOffice Dark Theme

I installed LibreOffice 6 Snap and it automatically inherited my Ubuntu 16.04 dark theme.

I installed LibreOffice 6 Flatpak and it does not automatically inherit my Ubuntu 16.04 dark theme.

Why? How do I enable the dark theme on my Flatpak LibreOffice?

I'm not sure whether we have the same problem, but for me, this helped:

sudo apt remove --purge libreoffice libreoffice-kde
sudo apt install libreoffice-gtk libreoffice

see also https://github.com/flathub/org.libreoffice.LibreOffice/issues/31 to see when the flatpack issue will be fixed

There is an active issue on the FlatHub's GitHub. They recommend running this command:

flatpak override --user --env=GTK_THEME=Adwaita:dark org.libreoffice.LibreOffice