cryptpad.org

I used Collabora inside Nextcloud for this.

There's Onlyoffice and whole ready-to-install packages bundled with Nextcloud around. One of them is Univention Corporate Server.

There's also Collabora based on Libreoffice.

Btw, look this up.

Nextcloud or Cryptpad

Look up Framasoft & use their tools:

• FramaForms
• FramaDate
• FramaPad
• Mobilizon

CryptPad, Collabora, NextCloud, Proton's stuff are great too

cryptpad and nextcloud are great

HedgeDoc would be another contender

Docs looks cool. I can't vouch for it though. https://docs.numerique.gouv.fr/home/ and it has a horrible name.

Which is part of https://lasuite.numerique.gouv.fr/

I'd use some markdown / typst processor.

Murena Workspace is IMHO the best alternative of Google Docs, OpenSource and made in the EU, Murena is also the author of NextCloud which has an collaboration platform, /e/OS and associated with FairPhone, a complete infrastructure privacy focused.

Proton Docs.

Please be aware that Google Docs the software is not the same with all those services running at Google's servers.

You can steal Google Docs' source code and run it on your own device, but somehow it won't work because it depends on reliable connection to Google's infrastructure. But anyway, that's the part of it where you can seek for open source alternative.

Mentions like Libre Office and the like is exactly that.

To replicate all Google Docs offers you, you need some rich and generous millionaires hosting a swarm of servers for you, for online documents, sharing to friends, collaboration and stuff. If you are looking for "open source" alternative for this, you are practically asking for free money. You either pay for it, or host it yourself. There's no free lunch.