I don't think it's browser specific or a direct targeting of Firefox; that's likely confirmation bias. I see rolling captchas and the annoying ones that have a delayed fading in and out even on Chromium forks. I think the biggest reason for seeing them is VPN usage. When I turn off my VPN, I either don't see any captchas or it just automatically shows the green check when I start them.

No problem :)

There's a FOSS fork of Signal which removes Google dependencies from the software.

Signal-FOSS

A fork of Signal for Android with proprietary Google binary blobs removed. Uses OpenStreetMap for maps and a websocket server connection, instead of Google Maps and Firebase Cloud Messaging.

https://github.com/tw-hx/Signal-Android

From a post on the GrapheneOS forum:

If you try to "update" it from aurora store, the update will fail because the signature does not match between the open source version you have installed as part of the system image, and the google version on store.

Its nothing to worry about, just ignore it.

Just add it to Aurora Store blacklist.

Strange. I haven't encountered any major quirks with it in my use. I've had app gave me trouble but it was because I had installed a pre-release version of the app by mistake, but once I installed the correct version, it was fine.

I will say one criticism of Obtanium is that it's easy to get rate limited if you use a VPN, which is really annoying.

While not an "app store" per se, Obtainium is pretty useful. It lets you manually import apps that you'd like to receive updates for, and can pull from different sources. For app discovery, I use Droid-ify.