Actually just reached out to the developer this week to try and resolve an issue regarding play integrity at their app. (email logs on request)
Turns out this developer has absolutely no intention whatsoever to bake in hardware attestation.,, furthermore, after I provided all the relevant documents and links to point out What could potentially be causing an issue with his app, he got very Irritated.
Without even reading anything, he continually insisted that GoS is to blame for the app not working. It's insecure, it's "modded or compromised" Not him or the way his app is coded. It quite literally Made me want To stop using the app and get a refund. I have no interest in wanting to use somebody's app who is that ignorant and unwilling to try and fix their service, especially considering that I literally told them that this app is recommended here, unofficially, but I guess I'll just come to the forum and let everybody know to go to something else, like QKSMS.
At least QKSMS isn't ABSURDLY RIDDLED WITH TRACKERS. CLOSE TO 125 of them.