Guarantee there will be questions of cost of setup, maintenance, and risks.

And time moderating it, especially if they run their own. At least with Twitter/Facebook/YouTube, you get a lot of moderation for free whether you agree with it or not.

And if they use another instance, there's other liability questions about the particular instance to choose. If they're gonna represent an official city account, you'd expect some cybersecurity certifications to be a requirement and all kinds of stuff, even if it's a free service. The instance admins interfering, possibly steering opinions during city elections, etc.

Nobody cares about decentralized social networks, the technology, or how terrible the other outlets are. For a municipality, you may want to focus on maintaining multiple channels of communications and ways to reach and engage the most users. You could then fold the fediverse into it as one more channel. Something they should keep an eye on. They'll need a way to post the same content to all those channels with the least effort. Something easy that a trained intern or clerk can do.

In this case IMO it might even be better to use something like Wordpress with the ActivityPub plugin, or alternatives to that. I imagine a city mostly posts announcements and stuff, so a blog that serves as both an official website and you can follow and interact with it from the comfort of your preferred social service sounds a lot more appealing than just another social media without that many users. Can even use more plugins to post to Facebook and Twitter as well, all from one place. Given the age of the board, they're also more likely to know and care about Threads and Bluesky compatibility just because they have more users, and bureaucratic decisions are based on numbers. A nice graph showing if they join the fediverse they capture all the users fleeing Twitter by supporting AP and AT.