I spent all day today debugging why the check subcommand takes a long long time for me with ~18k external links. (Result of that was Speedup "zola check" command by reusing the Client by MTRNord · Pull Request #2171 · getzola/zola · GitHub ).
I think it would be a nice addition to add a progress bar to the check subcommand to indicate that it is doing something and how far it is.
Locally I already made this happen, so if this would be accepted I can easily make a PR which uses an indicatif progressbar and looks like this:
The benefit of this is that you can clearly see that something is happening but also how far it is, how long it took and a rough eta when it will be finished. This helps debugging and imho is a better UX than just not reporting any activity.