I have had the same exact issues in Ubuntu Linux. One little oddity I've noticed and don't know how to fix while in Ubuntu is that I have to run NanoVNA-Saver with elevated privileges to actually connect to device ("sudo python3 nanovna-saver.py") to start. When it locked up, as it did in Windows 10, this time I saw a some type of message which I did not see in Windows:
Traceback (most recent call last):
File "/home/ubuntu/Git/nanovna-saver/NanoVNASaver/NanoVNASaver.py", line 702, in dataUpdated
The X11 connection broke: I/O error (code 1)
XIO: fatal IO error 0 (Success) on X server ":0"
after 984 requests (731 known processed) with 0 events remaining.
I had to force it to quit, so maybe that is all this is about, but it brought something up about "dataLock" I thought MIGHT have something to do with the lock up, I'm not sure though.