Creating A New Bootable External Hard Disk With Mac OS High Sierra On A Macbook Pro 2019 With Catalina

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Hey guys,

I'd greatly appreciate any help i can get with this.

I just bought a macbook pro 2019 with mac os catalina on it. I also got a samsung T7 the other day. I'm hoping to use the T7 as a bootable hard disk with high sierra on it.

I tried two things -

1) tried downloading high sierra from the app store after visiting this link -, but got the message the following message - 'Update not found. The requested version of macOS is not available.'

  1. downloaded a .dmg of high sierra 10.12 off this page -, I open the .pkg file but get a message saying 'This software is not support on your system'.

  2. downloaded an iso of high sierra off a website (not sure which one). This is the message i get when open the file and try to install it - ' “Install macOS High Sierra” cannot be opened because the developer cannot be verified. '

Please help me.