To be honest, this post is really designed as a reminder to me in case I ever reinstall my OS, but it will probably get a bit of Google juice and could possibly help somebody else.
If you’re using Digikam (a fine piece of software for organising your photos, well worth a look) and you find that it crashes on startup with Linux Mint, then
sudo apt-get install kdelibs-bin kdelibs5-data kdelibs5-plugins