https://support.apple.com/en-gb/guide/deployment/dep6fa9dd532/web dangles a carrot about being able to facilitate "A list of domains that the Shared iPad sign-in screen displays. The user can pick a domain from the list to complete their Managed Apple ID." - this sounds ideal!
In the absence of this seemingly being supported by Apple Configurator or iMazing Profile Editor at the time of writing, I have tried to create my own but I fall foul of knowing what PayloadIdentifier or PayloadType to use?
This is the draft/work in progress/doomed to failure config so far (which doesn't - as expected - work):
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>HasRemovalPasscode</key>
<false/>
<key>PayloadContent</key>
<array>
<dict>
<key>PayloadDescription</key>
<string>Configures Managed Domains</string>
<key>PayloadDisplayName</key>
<string>Domains</string>
<key>PayloadIdentifier</key>
<string>com.apple.domains.DE12211A-CFDD-4F8C-8D7B-72E569CE3B6C</string>
<key>PayloadType</key>
<string>com.apple.domains</string>
<key>PayloadUUID</key>
<string>DE12211A-CFDD-4F8C-8D7B-72E569CE3B6C</string>
<key>PayloadVersion</key>
<integer>1</integer>
<key>WebDomains</key>
<array>
<string>domain.com</string>
</array>
</dict>
</array>
<key>PayloadDescription</key>
<string>For Shared iPad login convenience</string>
<key>PayloadDisplayName</key>
<string>DefaultDomain</string>
<key>PayloadIdentifier</key>
<string>Tom.77CF3CA5-4A48-41DD-9179-EF6F4C5E786E</string>
<key>PayloadRemovalDisallowed</key>
<true/>
<key>PayloadType</key>
<string>Configuration</string>
<key>PayloadUUID</key>
<string>A5594F17-155B-4A1C-8696-3F502D118C37</string>
<key>PayloadVersion</key>
<integer>1</integer>
</dict>
</plist>
The support article is probably ~2-year old information so I'd have thought that by now that this would be documented somewhere - am I just not looking hard enough?