I just wanted to share my experience updating to catalina. After the upgrade I was able to connect using NoMachine, but I couldn’t see any windows, click anything, or use the keyboard.
To resolve this, go into preferences and Security & Privacy. I had to enable access for bash under Accessibility and Screen Recording. The server machine should prompt you that those requests are made, but it was hit or miss for me and I needed to restart NoMachine a couple times.
Providing details of the issues you have had will permit us to carry out investigations in preparation for supporting the final version when it is out of beta. You an submit these in separate topics on the forum or you can submit them via the website via the footer “Contact us” and select developer enquiries.