New 2019 iMac that came with Catalina...can I downgrade to Mojave?

[ghsDUDE]

Title says it all. New iMac came with Catalina but I’d like to downgrade to Mojave.

Wondering if this is possible since I already have a bootable thumb drive with Mojave?

Every time I startup in recovery mode and select reinstall macOS it tries doing Catalina again?

Any ideas on how to downgrade?

 

[Taz Mangus]

About Startup Security Utility on a Mac with the Apple T2 Security Chip - Apple Support

Use Startup Security Utility to make sure that your Mac always starts up from your designated startup disk, and always from a legitimate, trusted operating system.

support.apple.com

 

[Fishrrman]

iMacs (at least other than the iMac Pro) do not have t2 chips, so there is no "startup security" utility available on them at all.

Having said that...
See this post:
Can I downgrade new 2019 iMac with Catalina to Mojave?