After removing the libindiclient.so.1 file from /lib/x86_64-linux-gnu directory, I installed the today kstars/Indi updates. That fixed the problem.
Remote connection to the Pi4 server works now as usual.
Sorry Robert. Honestly I didn't mean any offence when I said 'a bit of a hack'.
However my wording was not ideal. I'll take better care next time. My fulltime job is in SW dev so maybe I was a bit careless compared to working in my day to day team.
Derek