I finally figured this out, at least for me: https://github.com/OpenAttribution/open-attribution/pull/201/files

I got it working by doing

market://details?id={google_store_id}&url=https://{domain_url}

So for example for my app: https://play.google.com/store/apps/details?id=com.thirdgate.hackernews

Which has it's .well-known at https://app.thirdgate.dev/.well-known/assetlinks.json

I first use the UA to check if the UA is from android, and then redirect to market://details?id=com.thirdgate.hackernews&url=https://app.thirdgate.dev

Which will correctly handle the deep link for if the app IS or IS NOT installed