How long does the “setting up your Mac” process take once download complete

If your Mac is stuck on the 'Setting Up Your Mac' screen

https://support.apple.com/en-us/HT204108

To resolve, press and hold the power button on your Mac for up to 10 seconds, until your Mac turns off. Then turn your Mac back on. Your Mac should now start up normally.

MiaziaLady wrote:

Just installed Catalina. Now stuck at screen that says “setting up your Mac” for at least an hour. Is this normal? What do I do!

An hour is a long enough wait—restart and see were you are.

You can force a restart by holding the power button/touch ID button for ~6-10 secs.