based off this answer, how can this be done in iperf3. Going through the iperf3 man page and documentation, it seems that the -t option no longer exists. What other ways can I implement to kill the server process after some duration or if no clients exist for some time? Is there a better / easier way than running a bash script in the back ground to kill the server after a certain amount of time?
There's no way currently to make the iperf3 server die after some amount of time, or if no clients exist.
The link you posted mentions wanting to make an iperf2 endpoint finish after a test. iperf3 supports a --one-off flag that causes the server to do at most one test and exit.