I guess the App is filtered for you then - AppLounge is using the same google-play API Aurora introduced - Unsupported app! in App Lounge - #23 by luc_pcm (see conclusion at the end) … it might be a bug if it’s filtered for invalid reasons though.
You can grab the appid apk from somewhere and try a streamed install via adb. Just make sure to check and compare the apk signature on it if it’s widely used, that good enough.
For a Moto Harpia the appid is filtered - so some filtering is going on, it might be device or region based - Barclaycard Deutschland not available (#669) · Issues · Aurora OSS / AuroraStore · GitLab