Still no fix for you but I have seen that sort of error message before. It might / ( might not ) be the XSANE version.
/home/rich/.config/GIMP/3.2/plug-ins/xsanecli/xsanecli.py-x:104: Warning: g_error_new: assertion 'domain != 0' failed
Gimp.main(XSaneCLI.__gtype__, sys.argv)
That comes from my old laptop, kubuntu 24.04 and at the time of installation XSANE just did not work at all. Not stand-alone, not with Gimp. I use a patched, compiled version which at least runs stand-alone, so I put up with scan-to-file, then open file in Gimp.
I know zero about Arch based distros but maybe ask if there are other versions of XSANE.
/home/rich/.config/GIMP/3.2/plug-ins/xsanecli/xsanecli.py-x:104: Warning: g_error_new: assertion 'domain != 0' failed
Gimp.main(XSaneCLI.__gtype__, sys.argv)
That comes from my old laptop, kubuntu 24.04 and at the time of installation XSANE just did not work at all. Not stand-alone, not with Gimp. I use a patched, compiled version which at least runs stand-alone, so I put up with scan-to-file, then open file in Gimp.
I know zero about Arch based distros but maybe ask if there are other versions of XSANE.