Where to download different versions of macOS

• 10.7 Lion https://www.apple.com/shop/product/D6106Z/A/os-x-lion (Paid, $20)
• 10.8 Mountain Lion https://www.apple.com/shop/product/D6377Z/A/os-x-mountain-lion (Paid, $20)
• 10.9 Mavericks: WRONG https://updates.cdn-apple.com/2019/cert/041-84842-20191010-6cd58113-6c02-49ec-8f4b-9557ecd838c2/OSXUpdCombo10.9.5.dmg (Combo update)
• 10.10 Yosemite: WRONG http://updates-http.cdn-apple.com/2019/cert/061-41343-20191023-02465f92-3ab5-4c92-bfe2-b725447a070d/InstallMacOSX.dmg (Combo update)
• 10.11 El Capitan: https://itunes.apple.com/app/os-x-el-capitan/id1147835434?mt=12
• 10.12 Sierra: https://geo.itunes.apple.com/us/app/macos-sierra/id1127487414?mt=12
• 10.13 High Sierra: https://itunes.apple.com/us/app/macos-high-sierra/id1246284741?mt=12
• 10.14 Mojave: https://itunes.apple.com/ru/app/macos-mojave/id1398502828?ls=1&mt=12
• 10.15 Catalina: https://itunes.apple.com/am/app/macos-catalina/id1466841314?mt=12&l=en-us
• 11.00 Big Sur: https://itunes.apple.com/ru/app/macos-big-sur/id1526878132

Source: https://support.apple.com/ru-ru/HT211683

It is also possible to fetch some of these via command line:

• 10.13 High Sierra: /usr/sbin/softwareupdate --fetch-full-installer --full-installer-version 10.13.6
• 10.14 Mojave: /usr/sbin/softwareupdate --fetch-full-installer --full-installer-version 10.14.6
• 10.15 Catalina: /usr/sbin/softwareupdate --fetch-full-installer --full-installer-version 10.15.7

Create install media

sudo "/Applications/Install macOS Big Sur.app/Contents/Resources/createinstallmedia" --volume /Volumes/MyVolumeName

Source: https://support.apple.com/ru-ru/HT201372
More links: https://support.apple.com/en-us/HT211683