Dino (XMPP, https://dino.im) is a great desktop client to talk to other XMPP clients, in particular Conversations, due to its broad support of XEPs.

Conversations has an issue where the main tool for reading a backup on a computer (ceb2txt (so, say, I can properly and correctly archive a text dump archive of a person I loved who died)), will not work for me. I filed a support request and there's been no movement on it whatsoever and it genuinely seems like nobody gives a shit. Restoring a backup even with all the images and media files in the correct place with the correct filenames will then refuse to show any filenames.

This is par for the course with chat backups, though.

Messenger - Bad - No way to save chat responses of people you have talked to. This means you only ever have one side of a conversation, making it meaningless.

Twitter DMs - Bad - See Messenger.

Jami - Ehhhh - Saves a git local repository of messages. The only problem is message syncing is effing abysmal.

Dino (XMPP) - Bad - Does not allow backing anything up, this is "intentional". Depending on which protocol you use, as soon as you move to another device all the messages you _had_ are retroactively converted to Cannot Decrypt. They're my effing messages!

Discord - Good - Discord History Tracker (tedious to use but slurps everything up into a sqlite3 database that is itself, an official archival format)

WhatsApp - Good - Dumps a text record + files/images/etc. onto the phone's filesystem. This is reasonably easy to archive.

Signal - Mediocre - If you have an old Signal backup from 2018? That you could only transfer off your phone by deleting old messages? lmao you're effed. Load up a version from ten years ago, gradually update it and then maybe, MAYBE you can extract the sqlite3 archive? These days you have a .signalbackup or whatever which is an encrypted archive, and I assume that there's a tool to decrypt it, but uhhhhhh. Last I tried to use it it required way more RAM than I had accessible.

+1 for Deltachat