I agree with the petition, but I wish it had mentioned that Twitter hides most, if not all, of an account's tweets behind a login wall. Same for Instagram for that matter. That's a strong reason not to use it for government communication.
Our regional police uses Twitter, and since I don't, I have to use some complex-ass relay through a third-party Mastodon account that I read through an RSS feed (because I don't Mastodon, either!)... it's not cool that official, important messages are put behind the wall of a private platform.
I think an actual official government instance would be a good idea. Probably Mastodon would make the most sense, since it would mostly be one-way announcements. With federation, easy enough to get that viewable wherever it's needed.