I don't know what {{ base_url($fthread.image) }}
is, but it looks like it's not using XenForo's abstracted file system/paths, which is a big no-no. You can't even be sure a XenForo installation is using the local data
directory, that's simply the default. A site could choose to use mysupercool/data/folder/for/stuff
if they wanted. So if that addon is hard-coding the external data URL portion to anything, they are doing it wrong.
They may want to look at how "normal" things like avatars and attachment thumbnails are referenced by XenForo, and go the same route. Look at the applyExternalDataUrl
and applyExternalDataUrlPathed
methods in \XF\App
.
If the addon is using the abstracted file system to upload things (and it ends up on R2 or whatever other filesystem you are using), it seems really strange they wouldn't also use the proper methods given for generating URLs.
TL;DR
If a third-party addon isn't following XenForo's standard abstracted file system conventions, there's not going to be anything we can do on this end.