I expect it's worth looking into the ActivityPub Fediverse, or the applicable IndieWeb protocols (e.g. the linkback quartet: refback, trackback, pingback, and Webmention), to measure what people are saying. None of these have global feeds, though, so you have to deal with the conceptual complexity of measurement. (You have to deal with this anyway with Twitter, because of bot activity, but it's easier to deal with "this is an upper bound" than "this estimate may be too high or too low, and we'd have to investigate further in order to find out which".)