CollaboraOnline explains the importance of this request very clearly:
https://www.collaboraonline.com/blog/a-brief-history-of-file-formats-doc-vs-docx-vs-odf/

I have several clients looking for a way out of the MS/Google office duopoly. There is no way I can convince them to move away without a committment to open standards - this is a major blind spot in Proton's offerings. Some sort of triple-shuffle between Proton, Libre and Microsoft kind of misses the point, don't you think?

Definitely agree. Support .odt asap.

This is already implemented for Sheets so it has been edited to just refer to docs. Thanks.

Yes, the proprietary Proton document format is simply a bad idea. Not everyone uses Proton!

For all of us who are running Linux and using LibreOffice (or any other open source office documents package), it is absolutely essential to support (create/preview/save as) ODF (not only .odt, but also .ods and .odp) within Proton Drive!

I can't understand why OPF is not supported in the slightest by Proton ecosystem. Not just that any person concerned with privacy is going to prefer it, but also that being fully open source and designed for portability, sound likely easy to integrate.

I feel that it is important to be able to open your docs that are synced with your laptop when you are on the move.

Duplicate, and not currently possible to implement per this thread: https://protonmail.uservoice.com/forums/932839-proton-drive/suggestions/50778653-preview-and-open-odt-opendocument-text-files

If you support and live open source, you should also support ODF and not just Microsoft's docx.

This makes the ecosystem even larger and allows for more flexible exchange.

Super important, especially for people trying to get away from generic big tech but have been surrounded by generic brands like Microsoft and Google (Drive) their entire lives.

Alternatives to big tech programs exist, but they also should be accessible on platforms like Proton Drive!

This is important both for exporting from Docs and to generate previews from odt documents in Drive.

ODF is to documents what the E-Mail standard is to communication. Proton should supprot it 100%

Yet another proprietary document format is a complete non-starter for my team and our clients. I won't use and won't recommend Proton Drive as a replacement for Google or MS One drive for clients that want to use collaborative web editing.

Completely agree with this. .odt format is preferable for me as some applications on my phone won't let me edit the document if its in .docx format, whereas if it is in .odt format they work great, hence I believe it would be a great way to improve compatibility.

Proton Docs should definitely use open document as default. Being able to export to other formats is a good feature but the default format is the most important thing. Using its own file format the same way Google does makes me chose Microsoft Onedrive instead. They let you chose default file format (Microsoft's or Open Document) when creating documents.

I use exclusively Linux for all my work and .ODT format is very important for me. Not being able to at the very least view the content with Proton Docs means I cannot use this feature.

I try to go away from the big tech and work under Linux. Not being able to open .odt documents in proton drive makes things unnecessarily complicated.
Please support open document formats

Proton docs should have the option to save files in .odt format. It doesn't make sense to save in .docx format and then have to convert it. I hope the .odt format becomes increasingly popular around the world, and Proton can't be left out. Attention, developers!

Proton uses the .protondoc format, you can convert a .docx file to the .odt file with a file converter.