Playground
This page lets you experiment with manifests from different providers, or you can provide your own with the “Custom URL” option.
Note that not all the options work for all the providers! So if you get an error, or it does not work as expected, then try something different.
The Bodleian manifests are good examples of requesting V2 or V3 Manifests through Content Negotiation. The BSB manifest has multi-lingual values to experiment with viewing the manifest metadata with diffeent labels. The e-codices collection shows off the Diva.js collection browser.