Downgrade Catalina to Mojave - Catalina Original OS

If I purchase a Mac that shipped with Catalina, can I downgrade it to Mojave? I am looking for someone that has actually done this. I have software that will only install on Mojave or earlier, then I can roll it forward back to Catalina. I would just like to know before we make a large purchase of Macs.
Downgrade Catalina to Mojave - Catalina Original OS
 
 
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