High Sierra install without App Store

Background: New mac running Big Sur macOS 11.4

Goal: Need to run xcode 9.3 to make changes to an old app

Steps taken thus far:

1. Learned that I xcode 9.3 will run up to High Sierra
2. Learned that I could create a 2nd APFS volume and install OS there (https://www.macworld.co.uk/how-to/dual-boot-mac-3659676/)
3. Attempting to get High Sierra from App Store but can not due to it being an older version

Issue: need to be able to download high sierra or any other OS installer to the second apfs volume without using the app store so that I can utilizing xcode 9.3

Assistance greatly appreciated