I\'ve created Firebase Dynamic Links in other projects before using the page.link URL prefix (the only option at the time). However that no longer appears to be an option when e
Everything you are doing looks correct with regards to getting your custom domain working. I am wondering if you are using the latest version of firebase-tools (CLI). Custom Domain support for dynamic links was added in version 6.5.0.
Good news is that page.link support still exists but is not as obvious in the new UI flow. The way to get a page.link domain is to start typing your desired subdomain and a suggestion should pop up in the UI. I have included a screenshot to show how this would work.
Adding page.link domain
Hope this helps,
Jeff