Hello again,
after an update of libmypaint-1.5.1-2 , gimp does not start no more:
gimp: error while loading shared libraries: libjson-c.so.5: cannot open shared object file: No such file or directory
I will try to reboot the computer and/or wait for an update .. not sure what to do else. Can't downgrade the libmypaint-package because I cleaned the pacman cache yesterday.
Ok, another update brought the package json-c-0.14-1, now gimp is starting again.