The Portable Freeware Collection Forums

There is no topic about Delta Chat in TPFC forums, even though it claims (experimental) portability.

Delta Chat is multi-platform (Windows, MacOS, Linux, Android and iOS) and FLOSS.

Regarding portability, although the single executable desktop version did save files to a 'DeltaChatData' sub-folder, my hopes are not very high, as I was able to confirm it is Electron-based by looking at the project's Github page -- but anyway here it is (posted tentatively to "Discussion").

Delta Chat is like Telegram or Whatsapp but without the tracking or central control. Delta Chat does not need your phone number. Check out our privacy statement. Delta Chat doesn’t have their own servers but uses the most massive and diverse open messaging system ever: the existing e-mail server network. Chat with anyone if you know their e-mail address, no need for them to install Delta Chat. All you need is a standard e-mail account.

Delta Chat desktop latest portable (untested!) release (currently v1.1.15) can be downloaded from https://get.delta.chat/ -- choose "Get portable version (experimental)" link).

GMX Mail is free and allows IMAP fwiw - also it didnt require an actual legit phone number when i signed up - afaik most of the big names in free email with IMAP do require some kind of phone number to send a text for verification