How to connect Unity to a diff tool on linux

I use unity with my team. I am the only one on linux. We use collaborate and sometimes there are merge conflicts. I therefore would like to set a diff tool to resolve these conflicts. However I am not able to do so via Preferences > External Tools > Revision Control. I have installed DiffMerge, TkDiff and P4Merge but Unity seems to be unable to locate these programs. How do I get unity to recognize it?

I installed meld through ‘apt’ on Ubuntu 18.04 and after restarting Unity, it picked it up.

Would be nice if it would be more flexible like the external c# editor settings.