Usually I install NGSolve via
sudo apt-get install ngsolve
and continue the installation of ngsxfem afterwards. Unfortunately, it hasn’t worked today, and I think because of the incompatibility of the outdated ngsxfem and the current NGSolve.
So my question is the following: how do I install an old version of NGSolve, for example, NGSolve-6.2.2101?