Yes, you can easily trigger the signer by using the standard nostrconnect:// uri scheme. That's what a "Login with Nostr" button should do.
We even added support for a convenient "callback" parameter, so Primal will redirect back to your app immediately after establishing the remote connection. If it's a browser app, simply use callback=https://[your_app_login_progress_page] to get redirected back to your app.
nostr:nprofile1qyxhwumn8ghj7mn0wvhxcmmvqy08wumn8ghj7mn0wd68yttjv4kxz7fwv3jhyettwfhhxuewd4jsqgplwuxkt5a8vj5utj6s8tsj8e3wcavc45p4mqmw92qs7wrh5azmys9f0hy6 implemented this flow for some of his web apps; it works great. Derek, maybe you could share a quick video of this in action?