matrix-viewer

Matrix has/had a great archiver at https://github.com/matrix-org/matrix-viewer - but it fell foul of the bizarre failure mode that folks who had explicitly set their rooms to be archivable had subsequently forgotten that they had, and then went absolutely berserk when they discovered their rooms having been archived: https://matrix.org/blog/2023/07/what-happened-with-the-archi.... This was one of the reasons given for libera to turn off the libera<->matrix irc bridge. At the time we had much bigger problems to deal with, so we shelved it and have yet to get back to it.

And https://github.com/matrix-org/matrix-public-archive

(heads up that we're about to replace matrix-static, which powers view.matrix.org, with https://github.com/matrix-org/matrix-public-archive - which is a way better public archive interface for Matrix, built on Hydrogen)

Matrix has view.matrix.org, and also has read only view of public rooms as per https://app.element.io/#/room/#matrix-dev:matrix.org (which should work if you’re not logged in). Meanwhile we’re also applying the Gitter approach to the whole Matrix ecosystem: https://github.com/matrix-org/matrix-public-archive