Not my project, but I'll ping it over to Dmitry.

One thing is that it's possible that Ellx uses exceptions to detect time series and lift regular functions into time series functions. I'm not sure the implementation details. There are all kinds of ways exceptions can be abused to implement near-magic. (I believe there's a library that uses exceptions in OCaml to implement coroutines.) I wouldn't be surprised if Ellx used some try-catch near-magic that doesn't quite work on Safari.

Creator or Ellx here. The reason is quite prosaic: I haven't maintained the site for almost a year :/ For various reasons. However, I'm getting back at it now. Ellx as a framework has evolved during this period, and is capable of much more than just a spreadsheet now, but this progress hasn't made it to ellx.io just yet. May I ask what you liked most about Ellx? What is your use case?

My use case is a tool that produces living documents mixing writing with charts, data, and tabular results that can be delivered to nontechnical clients and updated and modified by staff with excel knowledge.

I’ve found various JS notebooks like starboard and observable JS to be the closest thing, but they’re really not there. PowerBI is a Microsoft solution but it’s dashboard focused.

This sounds pretty much indeed like something I made Ellx for. When you say the notebooks like Observable are "really not there", what exactly is the show stopper for you? Btw, please ping me on Ellx Discord: let's talk!