And they have also long had places for collecting persistent, searchable information alongside their IRC presence; usually public bug trackers and/or forums.

It has become all too common for a project to offer only Discord, which not only makes all community-collected information more or less ephemeral, but also locks it away behind some corporation's ever-changing terms and conditions, some of which are onerous.

GP's complaint is not that ephemeral chats exist, but rather that there is often nothing else.

Except there were open, archival solutions for IRC for projects to take advantage of. Are there any for Discord?

Sounds like you have to join the server to see the logs, something that was not required for IRC archives.