Thanks for the heads up on this Martin, and the workarounds.
I haven't had time to look into it yet. I did quickly try building JobeInABox on Ubuntu-18 but had other issues.
I'm not sure exactly what php-mcrypt is doing there, but I suspect it was required by the API-KEY functionality in the Code Igniter framework I use for Jobe. Have you tried your new server with API keys?
I'll look into all this when I next have some free time, hopefully at the end of our current term (4 weeks away).