FWIW I had only one crash on Catalina so far, but it was a severe one:
I started recording, switched a scene via the websockets plugin and then the whole screen froze with a corrupted image split in two halves. Could've been a graphics driver panic or something, but haven't been able to replicate it so far.
Apart from that crash, using multiple NDI sources, Logitech C922 webcam and multiple audio streams worked fine, including switching scenes all the time. I use my iMac for encoding only, so all the common issues with Syphon not being supported anymore and necessary loopbacks for desktop audio capture don't apply.
The log does report at least one memory leak during runtime though and there are other things that might by down to Qt or other Mac-specific idiosyncrasies that will take a longer time to fix.
How do I get Elgato OBS Link work again??