As per usual for the last two years I'm working on an open source spreadsheet engine called IronCalc. It is super exciting. We have a proof of concept at

https://app.ironcalc.com

In the last couple of months my partner and myself quit our jobs to work on that. I am pretty sure that in a year from now the world is going to have a fairly competent spreadsheet alternative.

My capacity is fairly limited but I am trying to build a community around it. Join us!

https://github.com/ironcalc/IronCalc