You could try the attached font-manager .deb (remember to un-zip it ) This is not the same as the fontmanager.app from the repo. A double click should start the package installer and pull in any missing dependencies. Take no notice of '..a newer version is available .. messages. see screenshot https://i.imgur.com/8qlskVw.jpg
In use: Once the fonts are scanned, Choose system and go down the list un-ticking the ones to disable. When you close font-manager log out and log back in to make effective. A list in Gimp rendered and much-much reduced. screenshot: https://i.imgur.com/GxU6jSa.jpg
Works here, no guarantees.
Edit: Actually, you can get it if you enable this 'buntu PPA (and there is an update)
https://launchpad.net/~font-manager/+arc...tu/staging
In use: Once the fonts are scanned, Choose system and go down the list un-ticking the ones to disable. When you close font-manager log out and log back in to make effective. A list in Gimp rendered and much-much reduced. screenshot: https://i.imgur.com/GxU6jSa.jpg
Works here, no guarantees.
Edit: Actually, you can get it if you enable this 'buntu PPA (and there is an update)
https://launchpad.net/~font-manager/+arc...tu/staging