Many thanks for the nice CLI!
I just discovered that it the elapi whoami command does not work with "old" API tokens that do not contain the ID prefix. The change in the token's pattern is discussed in this elabFTW issue. If the "old" token is provided, the CLI aborts and raises the following error:
PatternNotFoundError("No API token ID prefix found in API token string!")
There is no need to address anything, I just created this issue to inform other users that might run into the same situation. Generating a new token is the obvious solution to tackle it.