Problem with Unity in Linux

[Eleusis La Arwall]

I'm currently running Unity 5.4.1f1 with TextMeshPro and the latest PartTools on Debian 8 (yes it's a bit old I know). For a couple of month everything was working fine, just as I was used to from Windows. A few days ago Unity seems to have broken down for no apparent reason. From one day to the other the Inspector looks like this (debug right; normal left):

The Materials settings have entrys I've never seen before. Any attempts to fix this have been in vain. I've found a similar problem on the unity forums and reported my problem over there too. I was told that it seems like a bug, unless I have some strange editor plugin that is taking over somehow. So, before writing a bug-report I want to make sure PartTools is not the problem. Has anyone here encountered a problem like this or may even have a solution?

The strange thing is, beside everything looking messed up, it actually still works. I went through all the Element X entrys and the fifth revealed the name "_MainTex". So I've set the texture here, exported the model and KSP loads and shows it in the VAB.

Most likely I have to reinstall Unity, but I couldn't find Unity 5.4.0p4 in the linux releases. So I'd like to ask other Linux users: What unity version are you running?