Grist

Grist at https://grist.ravergram.club is one of the most powerful collaborative spreadsheet apps available. However it is much more than spreadsheets. It has a database underneath and allows you to use complex relationships and python formulas. Read more about it at https://www.getgrist.com/.

Other Spreadsheet Options on this Server

These all have simpler functionality and different UI's.

Ethercalc

Anybody can create quick sharable simple spreadsheets at https://pad.ravergram.club/.

Nextcloud

Those with accounts can create and share spreadsheets for collaboration at https://ravergram.club/nextcloud. This is a good option when you want to be integrated into the other functions in Nextcloud.

Cryptpad

Anybody can create spreadsheets at https://office.ravergram.club/ that are end to end encrypted. This is a good option for sensitive information you want to keep private.