Supposedly the two apps "BirdyChat" and "Hiket" are WA compatible. Both are waitlist only.
Even after searching for ~15 minutes, I could find no information about how to become such a compatible provider.
I hope this situation will improve drastically, but it also looks like Meta will do whatever they can to make it as hard and annoying as possible, as they don't want to lose market share. Disappointing.
I think that info is here:
https://developers.facebook.com/m/messaging-interoperability...
Search terms: whatsapp dma program
Disclosure: I worked for WhatsApp until 2019, which included detecting 3rd party applications and blocking them when they didn't follow (unpublished) specifications.
# Steps to interoperate with Messenger or WhatsApp
Note: Separate documentation and applications are required for Messenger and/or WhatsApp
Review: Review the Reference Offer, Developer Documentation Overview, and Application Guidelines above.
Apply: If you believe you qualify, complete the form that’s linked in the Application Guidelines.
Review: If you meet eligibility requirements, we will send you our detailed Developer Documentation under NDA for review of the detailed technical requirements for interoperating.
Sign: If you can fulfill the relevant terms and technical requirements set out in the Reference Offer and want to request interoperability, sign the Interoperability Agreement that we will provide to you.
Build: Start building interoperability.
Enable: Complete the milestones outlined in the detailed Developer Documentation to enable interoperability.
Launch: Work with Messenger and/or WhatsApp on a joint plan to launch interoperability.Luckily the user bridge works pretty ok.
Whatsapp as universal user interface.
Perhaps the start of instant messaging becoming more like email?
See e.g.: WhatsApp Messaging Interoperability - https://news.ycombinator.com/item?id=39633936 - Mar 2024 (146 comments)
"WhatsApp will become interoperable with other messaging apps in Europe" - https://news.ycombinator.com/item?id=46107109 - 01-dec-2025 - 88 comments
> Chats with third-party apps are only available in select regions and may not be available to you.
Even the FAQ page is geo restricted. What a shitty attitude.