Hi,
I recently did a fresh installation of Manjaro, and everything went ok, but I’m having some trouble with the gThumb app.
The thing is that I’m not getting support to open/display RAW format pictures (from a DSLR). I don’t know if I’m missing a package or something but, if I remember correctly, in other distros that I used this worked out of the box
Here is a screenshot:
I think the libraw package should be installed by default. You could also try to see if by installing libopenraw helps. Of course you will need raw-thumbnailer package too.