Kbin/Mbin is still the only platform(s) to try to bridge the two.
Moreover it seems to have better discoverability than mastodon Mastodon. I can type a word or phrase in the search bar on kbin and find "Mastodon" posts whereas I'm stuck viewing whatever is timeline trending on Mastodon proper unless I follow someone or can figure out whatever hashtag person might have affixed to their post.
Even with kbin being down a good 1/5 of the time it remains the best ActivityPub viewing experience (in my).