This is a second feedback, whereas I had previously only booted directly from the ISO in VirtualBox on somewhat modern hardware and created a Live-USB. This is about the live-usb. The live-usb created flawlessly (twice, because the first was to suspected-to-be-bad flash drive; it was bad).
The second 16GB live-usb (about the minimum size to allow space for remastering) booted quickly to 2008 AMD-X64 dual-core hardware with 4 GB or RAM. Enabled persistence with 3 GB static-root rootfs. Upgraded, installed openssh-server, x2goserver, and x2goclient. The XFCE desktop continues in this version to be unusable as a remote machine, same as MX-19. From a local login I installed LXDE with MXPI. Logging in to LXDE locally and remotely via x2go found it to be totally usable and nicely configured.
After a reboot and saving persistence, I rebooted loading the nearly 800 MB persistence file. I remastered, and rebooted again, then cleaning up old persistence files with MX RemasterCC. Currently concurrently logged in locally with XFCE and running remotely with LXDE as same user. Working fine. No conflicts observed. Default software appears to work fine.
I've been unable to discover any new bugs. For the curious, here is a link to a screenshot of the slightly tweaked LXDE desktp from a remote session:
http://2chronicles36.org/Screenshot_MX21b1.png