Actually European Commission has been on its own Mastodon server for a couple years:

https://ec.social-network.europa.eu/public/local

Signal does NOT send encrypted notification, they send a blank notification that act like a ping, the actual encrypted data is then fetched by the app itself.

Signal does NOT send notification content througth APN/Firebase, their push notification is literaly a ping as you expected.

Source: https://mastodon.world@Mer__edith/111563866152334347 (Meredith Whittaker is the current CEO of Signal)

I can't link you rigth now to the actual code on their repo but it is verifiable.

Btw I clicked your mastodon link and it didnt work

I was writing that maybe they're using one of their AI models to count, and we all know how they count.

3 work on my machine (Firefox 102 on Android 12) if the site is a PWA else it lets you to have a link in your home screen.

The option is "Add to home screen"/"Install app" in the menu.

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Also about 1: did you tried to put the bar in the bottom?

Firefox removed PWA support on desktop. It still exists on Android.