Roundcube mail is back. It is in the WebApps->Mail->Roundcube menu or the direct path is https://roundcube.eskimo.com/.
This is running on the new server and will be down between Wednesday evening and possibly Saturday though I may be able to get it back up sooner. I am replacing the motherboard, AGAIN, as the new motherboard is stable BUT has two dead memory slots so the machine is only seeing 192GB of 256GB of installed memory.
None the less, it is now an 18 core machine, 36 threads, at 4.8Ghz all cores.
The way I finally got roundcube working is that I installed Ubuntu 20.04 on a virtual machine on the new server. I have this virtual machine listening to a non-routeable IP address so that it can not be reached directly from the outside world to provide some degree of security to ancient software. Then I have it proxied through the main web server on the new machine which listens to both a public IP address and a private one that it can use to talk to internal servers. Something about 24.04 breaks roundcube, I know not what.