Thanks for the clarification about NoMachine. That is not necessarily a deal-breaker, but it is another inconvenience. While imaging with astroberry, I tend to keep an open vnc connection on the desktop on one floor of the house and the laptop on the other, but I'm sure I could get used to having to log in again more frequently. I will keep exploring vnc options. There is something fundamental I am missing, because I get the same error message when I try to start either tigervnc or tightvnc. There is probably some precursor installation I have missed.
I don't have a lot invested in the system yet, so I'm thinking about maybe starting over from scratch with an Ubuntu server install followed by a different desktop (you noted being forced to use Gnome - that comes from choosing the Ubuntu desktop installation option).
One thing I find clunky about Gnome for KStars is actually something the Gnome developers probably think of as 'elegance'.
In this first image of an astroberry install (not mine, I stole it from a google groups post, but mine is similar) you see how the various KStars component windows each have a Windows-style tab near the top of the screen. Switching from one to another is a simple matter of clicking on that tab. If I need to adjust something in the INDI Control Panel it is a single click to bring focus back to the control panel.
In Gnome, the KStars windows are organized as dots in the main KStars icon on the left. To bring the INDI Control Panel to the front you need to click on the KStars icon, then click on the pop-up window for the component you want. (you can also see in the screenshot where I don't have a minimize widget on the Mount Control window - which is a pain given that Mount Control is persistently on top).
I don't know if there is an Ubuntu desktop flavor that is more like the Debian buster desktop, but I'm looking.