There are no 1st Amendment issues with Amber Alerts or weather alerts pushed to my phone, for example. But if CNN or Fox News are allowed to post to this proposed service, now we've got a different animal.
And, if I may, I think the point is that is all well and good, but for reliability's sake, a publicly, not privately, controlled alternative to any of the above (Facebook, Twitter, Instagram, TikTok, WhatsApp, etc.) should be carefully considered. Mastodon is perfectly set up to be a valuable ADDITIONAL option for local governments using Twitter -- that doesn't mean "stop posting to Twitter," it means "also post to Mastodon" and be certain that, whatever shortcomings that may have, it's not entirely susceptible to the whims of a billionaire. Similarly, are Facebook posts by local government failing to reach users because of some change Zuck made to The Algorithm? Maybe we need to start looking into effective alternatives. If not, then we don't.
In my opinion, the biggest problem with an "ad-hoc" framework, or custom-built framework, is that there is definitely going to be less documentation for the next person on how to use that framework.
There are no 1st Amendment issues with Amber Alerts or weather alerts pushed to my phone, for example. But if CNN or Fox News are allowed to post to this proposed service, now we've got a different animal.