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No. Apple computers cannot install an older OS than what was originally installed (usually shipped with).
 
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No. Apple computers cannot install an older OS than what was originally installed (usually shipped with).

That is not quite correct.

While Apple does not support installing an OS that was released prior to the release of the machine, in some cases people have managed to get them to install, using various tweaks/hacks.

For example, Snow Leopard on a 2011 Mac mini. Somebody also managed this with a late 2011 MBP - unfortunately I can't seem to find the link.

The most likely candidate for Mojave among the 2020 13 rMBP models is the 2-port one - it uses the same CPU/GPU as the 2019 model, so in theory the drivers in Mojave should work. The 4-port model has a newer CPU/GPU. There's also a question as to whether the T2 chip will make things more difficult/impossible.
 
Thank you guys. Yes, the basic model seems to be a good candidate, but the one I'd consider would be the top 4-port one. I guess it's a lost case...
 
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