RSVPer
Wedding invitations and RSVPs that you run yourself.
I built this for my own wedding. Each household gets a short code, guests tell you who's coming in a minute or two, and you see the replies as they arrive. It runs on your own Cloudflare account, on the free plan, with no tracking.
Or try the demo: a made-up wedding you can click around, with no sign-up. Your changes are only visible to you.
Hosted version coming soon. If you'd rather not set it up yourself, that's on the way.