Note: Always backup your important files before doing such installation. My Macbook froze after first reboot, but after hard reset everything worked.

This procedure was done on Macbook Pro 15" 2015. Recorded on macOS 10.14 Mojave.
This Macbook has Catalina and Big Sur installed the same way as Monterey was installed.

To download the macOS 12 Monterey Beta you need to sign up for Beta here:
[ Ссылка ]
After that it will be downloaded as an update.

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