Until Crimson is officially released, you can use this:
gsettings get org.gnome.desktop.interface font-name
That will get you the current font name and size, e.g.:
Cantarell 11
To set it to something else, e.g. Cantarell 12 (or 13, 14, etc.):
gsettings set org.gnome.desktop.interface font-name "Cantarell 12"
[ref: [Solved] How to change GNOME fonts from the terminal / Newbie Corner / Arch Linux Forums]
You can also use the dconf Editor app to set the same, at:
org > gnome > desktop > interface > font-name
(Note that the native version of dconf Editor may be a little quirky to scroll; may not be a problem with the flatpak version. Select something toward the bottom or top of screen, then after the next level opens, go up one level to return to where you were, with additional entries now visible either at top or at bottom. Repeat if necessary.)