Post the Hyprland config too?
Does it make the entire screen green by chance, not just the windows? If the shader applies to the whole screen, then setting alpha on it doesn’t really makes sense and is probably discarded since your monitor can’t display transparency. You need to make sure it applies on a per-window basis for them to be composited as transparent and show your wallpaper behind it.
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.
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.