For the Puppeteer alpha release the name property needs to be implemented. Here the method to update:

https://searchfox.org/mozilla-central/rev/74cc0f4dce444fe0757e2a6b8307d19e4d0e0212/remote/domains/content/Page.jsm#115-126

I think the name field here is just mirroring WindowProxy.name.

Here what CDP is sending:

1. Navigation to a site without frames (mozilla.org) - no name is being added:

  puppeteer:protocol ◀ RECV {"method":"Page.frameNavigated","params":{"frame":{"id":"B368D7EB6FB371FFFA1B3D795750ACC5","loaderId":"8B9BA6366E22653895A69F660A6D9EA8","url":"https://www.mozilla.org/en-US/","securityOrigin":"https://www.mozilla.org","mimeType":"text/html"}},"sessionId":"367CDE3684BE3A070D69307F26C12003"} +0ms

2. Navigation to a site with frames (iframes example on MDN):

  puppeteer:protocol ◀ RECV {"method":"Page.frameNavigated","params":{"frame":{"id":"6BC7A5CB01867D4A7C111B0E9674565D","parentId":"6354A8C32B70C62617EB8A9EDDBE8D46","loaderId":"6E4AE60840FFAAA150751C282EBDF0E9","name":"inlineFrameExample","url":"https://www.openstreetmap.org/export/embed.html?bbox=-0.004017949104309083%2C51.47612752641776%2C0.00030577182769775396%2C51.478569861898606&layer=mapnik","securityOrigin":"https://www.openstreetmap.org","mimeType":"text/html"}},"sessionId":"E46199D8C6F9D3B6474C27366FA67775"} +0ms

So this is actually the id if the iframe, which is accessible via window.name as Andreas mentioned above. But to prove that we have to get bug 1593226 fixed first.

Actually the name property is not used in Puppeteer nor Gutenberg:
https://github.com/GoogleChrome/puppeteer/blob/master/lib/FrameManager.js#L232-L261

So not sure why I thought it is immediately necessary. Removing as blocker for the alpha release.

I might do that as part of bug 1637640.

Fixed by my patch on bug 1637640.