After some troubles with scripts and printing running the dt flatpak (v5.4), I decided to install another instance of dt from source (v5.4 under Linux Mint 22.2). So far so good.
To share the same configuration between the two dt’s, I just added the --configdir option when starting the non-flatpak dt and pointed it to the flatpak configuraton folder in ~/.var/app/org.darktable.Darktable/config/darktable/.
Now, for test purposes, I just made an image monochrome in the non-flatpak dt version (and it updated the view in the lighttable) and then closed dt and opened the dt flatpak version. Now that same image is monochrome in the darktable view, but the lighttable view still shows the color version. Only after manually loading the sidecar file is the view updated to monochrome. Is this a bug or for some reason expected behavior?