How to make VNC Viewer on iPad connect with Mac (Big Sur) Screen Sharing before someone logs in?

I would like to use my iPad with VNC Viewer via Screen Sharing to control my Mac Mini. However, I've discovered that VNC Viewer cannot connect with the Mac after it's turned on or rebooted until after someone logs into it. Once I login, I *can* access the Mac via Bonjour or the Address Book entry I made in VNC. The VNC error I get before logging into the Mac seems to indicate that before that initial login the Mac is not listening on the Screen Sharing port. I suspect I could work around this issue by enabling auto login on the Mac, but to do that I would have to disable File Vault, which I'd rather not do.

So, my question is: is there a way to get the Mac to start listening on the Screen Sharing port (5900, I believe) and accept screen sharing requests after the machine boots up and before anyone logs into it? I don't want to disable File Vault and I don't want to leave the Mac running all the time.

TIA