Looking at the screenshots, Delta Chat is a messaging app. Yet another messaging app, one might be tempted to say. Whatsapp, Messenger, Skype, Telegram, Signal, Discord and so on.
That would be true, and the regular functions are there: Chat, exchanging photos, audio messages, contacts. But the protocol is different. Delta Chat is in fact a mail client, you see.
It is an elegant... I hesitate to call it solution, but it is definitely an interesting suggestion.
Taking turns attacking centralised structure, the untrustworthy gatekeepers, the complexity of federated setups, data mining operations, encryption standards criticised by a disparate guerilla army of technologists with arguments impossible to assess by 99,999% - the messaging wars leave you tired and puzzled.
So the novel suggestion:
- Use an established protocol
- The app does not have to reinvent the wheel. Transferring files? They are just attachments. Attachments work.
- Trust the people you already entrust with your email with your chats, or someone else; it is, after all, not like you can not track down an email provider
- Send a message to someone not using the app, they simply receive an email. If you have turned on the encryption options, there are email apps supporting the same Autocrypt protocol. It will fall back to regular email Transport Encryption (TLS).
- Posted a link - that became clickable
- Inserted an image file from media picker - that inserted an image; there is also an option to grab from camera.
- Audio files uploaded render as a small player - unfortunately not the file name.
This file was recorded with the recorder button at the bottom, so essentially a voicemail.
- This was an upload of the Moonshine Sonata stored on the phone. Took some time to transfer.
- Last but least, a non-standard experiment: An epub file I had on the phone from Gutenberg.org. It is just email; this is just an attachment.
Of course you then get the restrictions imposed by email. There may be a maximum attachment size; some mail services may flag this kind of email or the message frequency; and it still works as a mail drop, so no live video chat: You record it and send it.
It is well executed. The application is modern and efficient, works well in Android, which is available from the Play Store and F-Droid. There is a beta-stage desktop client being developed for Linux and MacOS as well as a mobile app for IOS. I got it working with the provided Flatpak under Fedora 30: