On that thread a few of you asked for a self-hosted version. So I built it.
There's a free tier available. I put loads of effort into making setup easy - just one install command that gives you a CLI for start/stop/upgrade commands etc.
It runs as a single container, you can use a custom domain out the box for hosting over the internet (it provisions a LetsEncrypt cert for you), or just run locally (then via tailscale or whatever else if you want private networking). Single-player mode for private note-taking is indeed a much-encouraged usecase and is unlimited within the free tier.
This release also includes other big improvements requested in feedback last time (in both the self hosted and cloud versions): Export of notes; editor formatting more intuitive; easier to manage your actions.
Next on the roadmap is native clients, but honestly the mobile web experience is already quite usable. I use it all the time on my phone!
Give it a go, and let me know what you think :-) Any help needed with setup or anything else really, contact details are in my profile.