Migrate from an early 2015 MacBook Pro running Catalina to a 2019 MacBook Air running Mojave I have one early 2015 MacBook Pro currently running Catalina 10.15. That’s my production machine;
I got a new 2019 MacBook Air which I want to make my main production machine; The Macbook Air is from summer 2019 and came brand new with Mojave installed;


Is there a way for me to migrate from Catalina to Mojave, using either the Migration Assistant or a TimeMachine backup? If I a restore from a TimeMachine backup, won’t it also restore the Catalina version of macOS on the new MacBook Air?
This has already been answered here

Anyway you should be fine as long as you only import data, e.g. desktop, documents, downloads, etc.  I would not try to carry over ~/Library folder, as this may contain items that are only relevant to the 'newer' version of macOS.  You should probably separately export Apple Mail and re-import as well.

That being said... why don't you just first update the 2019 to 10.15 then directly import your time machine and not worry about incompatibilities?