Regarding webmentions, webmention.io (receiving) and webmention.app (sending) are excellent. If you prefer to manage your own like me, then you may find this glitch helpful: https://glitch.com/~lean-send-webmentions.

I've also written a complement to webmention.io which it can use as a callback hook to turn webmentions it receives into GitHub issues (great for if you use a static site generator). https://glitch.com/~webmention-io-webhook-to-github-issue