You can also try this for getting the iPhone 8 Plus installed:
When you create the simulator, if you tap on "OS Version" there is a drop down for "Download simulator runtimes", (which takes you to the "Platforms" settings screen, there is a little "+" icon there select "iOS" and from there you can install iOS 14.3 (which is 5GB) or another iOS version if you like, so your iPhone 8 Plus can run on that instead.
The don't make all of these buried drop-down screens with the little "+" icons easy to discover...
Topic:
App Store Distribution & Marketing
SubTopic:
General
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