The answer to the question about a "not default filesystem" affecting the running of any application is, it depends. Some programs are built with a certain path for, example, their shared libraries, cache directories (if any), config files, etc. Tcl/Tk is one example. It expects its system files to be in a specific place (e.g., shared libs). But I have a some external libs, including my own, under ~/tcl/lib and ~/tcl for others (in case someone here doesn't know, ~ is your $HOME directory, which, on this laptop, is c:/jim ... I'm going to start using that for most of the rest of this post). For those Tcl and Tk libs in ~/tcl and ~/tcl/lib/ all I need to do in any Tcl script is include one line telling Tcl and Tk where to look for packages I'm requiring.
LMMS certainly expects its own compiled binary stuff to be in the places where they were put during installation (when it gives you the option of where to install it).. The other files, VST, MIDI, etc., are located where you configure them to BE located in Settings-->Directories (click on Edit--->Settings and then choose that file folder icon). THAT is where LMMS will look for VST, MIDI, etc., files. You can use that to configure LMMS to look for VST files on a server on Mars if you have a link to a file server on Mars (granted, you'd have some terrible delays). In other words, LMMS looks where you TELL it to look. If you aren't familiar with how to use different paths to VST, etc., it's all in the documentation on lmms.io. Just check that out and it will become quite clear for you.
And to further explain that using the paths you specify in LMMS, even if not the default paths, works, actual VST files are working just fine, as I've been saying all along. They would NOT be if LMMS let you use your own custom paths and then insisted that your own custom paths be restricted to its defaults. But why would any open source app do something so stupid? Answer: it wouldn't. Someone could try to inflict an idiotic rule like that, but you'd then have a flood of other devs demanding that bug, and yes, it would be a bug---a self-inflicted bug, but a bug just the same, be fixed IMMEDIATELY.
The so-called "non default" paths that I'm using are all defined in LMMS's settings-->directories, thus making them the default for my system. If that's not clear enough, see
https://docs.lmms.io/user-manual/gettin ... irectories.
A "non default" path would be one where I set the path for VST plugins to /foo/bar/VsT-UseThis and then instead, I put everything in /home/jim/VSTplugins (tired of typing M$ paths). But if I put them in /foo/bar/VsT-UseThis, as (hypothetically) configured in LMMS, that would then be the default. In other words, the default is what YOU configure in LMMS. That's why that whole section of settings is there in the first place.
I think I deleted this part when taking out a big chunk of this.... Note that I am NOT saying that nothing is working. The actual VST files are working fine, installed in the path that I configured in LMMS's settings. It's ONLY the MSE "VSTs" that aren't working. For that to be true, LMMS is clearly looking where it's configured to look. It just doesn't seem to like one of two types of so-called (by VST sites) VST files.
So can we please, IF this topic is going to be continued, look at those MSE "VST" files that are not working, and try and find out why they aren't working? As opposed to wasting time on why LMMS allows you to configure directory paths for where you put different types of files and then demands that you follow those "factory default" settings? If you want to continue that argument, please point out the specific source file(s) and the line(s) in said file(s) where it forces you to use hard-coded paths and ignores your own paths as defined in LMMS's directory settings. I will then submit that as a bug.