Just to be completely transparent here - the trial license has a hard time activating in docker due to the way that docker virtualization clashes with the license manager's attempt to uniquely identify a server.
If you would like to try running RStudio Connect in a docker container, and the advice above doesn't get you functional, I would recommend contacting our Customer Success team at sales@rstudio.com . They can get you a trial license that will work better inside of docker (either floating or not). We have some patterns that you can follow here:
https://docs.rstudio.com/connect/admin/server-management.html#server-docker
TL;DR; Connect works fine inside of docker. However, the trial does sometimes have some trouble activating inside of docker. You are still completely eligible for the 45 day free trial, though! It just needs some input from our team to get it working, unfortunately
Hope that helps!