Which extra repos are safe to use?

[uhlenspeegel]

Hello,

I finally managed to get Exagear working the way its supposed to on my ARM device, with Ubuntu 16.x as the guest OS.
But I found out, that when I add extra repos and perform an upgrade, I might end up not just screwing up Exagear but the host OpSys as well ("too many symbolic links" -> nothing works anymore).
So is there a list of what repos are safe to add and most importantly, what *not* to install - so to to protect Exagear and the Host OpSys?