I recently tried Collabora and found it to be laggy on my Pixel 7. I hope they find a way to fix that because I like the app otherwise.
I've been using MS Office (Word, Excel, Powerpoint), but specifically version:
16.0.17126.20038
com.microsoft.office.excel
versionCode 2003820419
The reason why is because this is the last version before they made signup/accounts a requirement to use their apps. This version, the user can skip Sign In and use the app completely including new documents, editing and saving.
After a fixed interval ( I think a half dozen or so runs of the app) the app forces the user to finally sign up/sign in. But all you need to do it clear the app memory/cache to reset the app and you can keep using it. Rinse and repeat.
Network permissions can be killed with no impact on the app.
Once installed, avoid updating it.