I can confirm that you don’t have them installed.
I’ll have to reinstall Ubuntu MATE on my laptop, I’ll do a quick test with GIMP.
EDIT: ok, I could replicate the issue. On a fresh UM 18.04, I had the idea of installing GIMP from the Software Boutique (which I never do, I’m so used to the command line that I manage my softwares directly with APT), as I realized you probably used it in the first place. And there’s something weird in the installation of GIMP from the Boutique. For some reason, it also installs:
- gimp-gmic
- gimp-plugin-registry
- gimp-gap & mplayer
And as it seems that the GIMP package from Otto Kesselgulasch’s PPA include files that are in the gimp-plugin-registry, the process breaks. I’m not sure if it’s a decision from him or if GIMP 2.10 added some new plugins that were independant before.
And the fact that it worked when you followed some of my instructions using command line is because they simply installed GIMP, no extra packages.
I’ll report the issue to him but it might be worth looking why GIMP from the Boutique installs extra packages. It’s likely a choice by the UM MATE developers (as softwares in the Boutique are more or less manually curated).
EDIT: so, until this is sorted out, if you want to install GIMP on UM 18.04, you have these possibilities:
- Stick with GIMP 2.8 if you install it from the Software Boutique.
- Install it manually rather than using the Boutique if you want to use GIMP 2.10, either through Synaptic or APT, by installing only the gimp package. In that case, it doesn’t matter if you install GIMP first then upgrade, or if you add the PPA first (but in any case, don’t install it from the Boutique while using the PPA).
- If you want to install it through the Boutique but still upgrade to 2.10, be sure to purge the gimp-plugin-registry package before adding the PPA.