Through my kDrive subscription, I get access to their own instance of OnlyOffice

It looks a bit dated like MS Office, but it does the job and since it used MS Office formats, I can edit the documents with Libre Office or other sofwares. And using the API, I can programatically access those files.

https://www.infomaniak.com/en/ksuite/kdrive

https://www.onlyoffice.com/

I just developed a webapp for it. I only used Docs for personal reasons, so my own version is basically just a really stripped down rich text editor. A lot of things I just save to .txt files.

It saves (both locally and to self-hosting) to JSON and, exports to PDF and HTML. And then I wrote a script to convert docx files over when I migrated from Google.

I just use any scripting language, mostly Typst, because then I have the analysis directly in the document

Microsoft Word and Microsoft Excel?

.xlsx is the key. Can use it with sheets, M$ or libre office. Or unzip it and take a look at XML.

same problem?

Obsidian with Syncthing works great for me over Docs.

Haven't found a good self-hosted Sheets alternative yet.