As you can see I have tried multiple different versions. I am using a 64bit xubuntu distro. Currently, I am still using lmms 1.1.3 as it is the only way I can get work done. When trying to load a VST on 1.2 RC4/5/6 it says "loading" and then nothing. Vestige still asks me to load a VST. If I open a project created in 1.1.3, it loads fine and plays fine but the moment I try to load a new VST the same thing happens. Surely I can't be the only person with this problem. I just hope it gets sorted out before the final 1.2 release as, if not, I will be stuck using 1.1.3 for the foreseeable future.
Vst working fine for me on openSUSE, lmms rc 5.
I am using the appimage from the download page. ( there is a even newer version there )