Just a thought…
Have you considered open sourcing the spreadsheet.com source code and publishing it on Github?
That would be a great option for the people that currently use spreadsheet.com and would like to continue using it. I’m sure some people from this community or others that hear about it changing to open source would be able to pretty quickly come up with a solution for anyone to self-host or just run locally. Most likely using docker for people to more easily get it running on their PC.
It could turn a failure into a big win in the long run. Open source communities can build some amazing stuff. I would love to be part of an open source version of spreadsheet.com I can self-host.
“Failure is not the opposite of success; it is part of success.”