How to check how many users are using Horde webmail?

Hello guys. I have a question. Since Horde support will be removed in the new version 108, I would like to know if there's any method that I can check how many of my users or domains are using Horde webmail service so I can inform them about moving to Roundcube. Can I run a command line or grep in the logs something. In this case I will need something handy so I can check even logs from month ago or so.. Thank you in advance!