Yeah. Mobile phone alerts are probably about the best you can do these days beyond going house to house (and even then). You're never going to get to 100%. But, as you suggest, Twitter isn't even a particularly good channel. I use Twitter and I have no idea what my local government channels are, if any.

Even if you don't use it, you can check it during an emergency. Even if you don't check it, someone else else was checking it and relaying that information to you. You used to be able to search an account on an app you already have, and get the latest information. Now governments have to manage their own instances, you have to search their website, find the url, subscribe to it or download a custom app, and then you can finally see what used to be a search away from you.

That can only be described as a loss.

I can't get used to either Twitter or the fediverse, but they don't work differently on the discoverabilty aspect.

One would likely just subscribe to your city's hashtag for large cities or to your town hall's account for small ones, and that's all. The rest works like Twitter (except there is less risk of important posts getting invisibilised by the feed algorithm).

In my fediverse test, I just subscribed to #Antwerpen (as well as #Antwerp and #Anvers but that's a whole other problem...) and I did get relevant and interesting posts. In their small town my parents are subscribed to the town hall's Facebook account (the only reason they signed up to Facebook) and it would work the same on any other app, except it likely would spy on them a bit less. Mastodon's Android app is not a "more custom" app than Twitter or Facebook's apps are, on the contrary I would argue.

I just can't get used to checking this thing more than once every few days and like Twitter it just doesn't work if you're not constantly reading your feed, because then you're missing most posts.