@aral Also, Firefox and Chromium probably interact with Orca differently under X11 versus Wayland (and native Wayland apps vs X11 apps on Wayland too).
Using the X11 versions on X11 is most likely the best combo for now, due to the length of time it's been around. Hopefully Wayland will keep getting better a11y support as time progresses.
For centralized a11y discussions, there's gnome-accessibility-list and gnome-accessibility-devel mailing lists and #a11y on irc.gnome.org. More details @ https://wiki.gnome.org/Accessibility
@aral You can also just run "flatpak update" at the command line to fix this if it doesn't work.
Flatpak is aware of themes and tries to install the correct theme if it exists in flatpak form.
(I suppose a case where an available theme doesn't match is when there hasn't been a flatpak update since a theme changed to one that didn't have flatpak support installed.)