That's the problem with canaries, though. By definition, they exist for situations where the canary-owner can't offer positive evidence for compromised security.

I don't particularly think Riseup is in that position, but unless someone actively says "don't worry about our lack of a canary, we took it down for $REASONS and all is well", negative evidence is all you can react to.

It could have been an attempt at plausible deniability.

Have you happened to see their other messages from the same day?

"Dear friends, please remember that internet is not always the answer..."

"by the way, that wasn't a trump related tweet..."

"listen to the hummingbird, whose wings you cannot see, listen to the hummingbird, don't listen to me. #LeonardCohen"

It all "has nothing to do with" canaries.