I've been playing about with the latest appimage for linux and have found a couple of FEM issues. I could not find any references to the issues on the github bug page, but thought I would raise them here first.
A) FreeCAD_0.18.16027_Conda_Py3Qt5_glibc2.12-x86_64.AppImage does not seem to have the ccx binary included. - Fairly self explanatory. Easy workaround to specify the path to an external ccx in FEM Preferences. I don't know if there are any version dependencies for ccx tho', so I don't know if this is a good workaround or not. The ccx binary was included in the FreeCAD_0.18.16000.glibc2.17-x86_64.AppImage
B) FreeCAD_0.18.16027_Conda_Py3Qt5_glibc2.12-x86_64.AppImage crashes with stacktrace whenever the 'Use FreeCAD material editor' button on the Model -> Material -> Material for Solid task panel is clicked. Looking at the stacktrace my guess would be this is a Py3 issue, but I'm a long way from a python expert. Workaround seems to be to use material already in the stock database. This did use to work on the FreeCAD_0.18.16000.glibc2.17-x86_64.AppImage
I can write one of both of these up as bugs on github if that will help.