Installed Boinc on Solus because they don’t have a native package yet.
This is a common problem. Too many packagers/packages don’t test with the VirtualBox projects. I do have Virtualbox installed.
Ubuntu has a special Boinc Virtualbox package just to fix these issues. Just saying the flatpak is going to probably have to do the same thing.
LHC is a good project to test with because it seems to be the most sensitive.
If memory serves, this is more a “rights and priv” issue. Something about Boinc not being able to write to the directory where it is installed when being utilized by a project. This has been popping up for years.
There is a semi-official hack that works some of the time for some of the distros.