Unfortunately, this seems to be the only option, besides using your own domain so that you control forwarding yourself. Basically, pay someone like Firefox Relay to do forwarding, or do your own forwarding. Firefox Relay does give you five email addresses for free, which is cool. (https://relay.firefox.com/#pricing)
I've noticed that the "+" sign trick with Gmail just doesn't work at all anymore. Anyone that wants to maliciously send you emails knows to remove what comes after the + sign, so that you can't tell which of your sub-addresses was originally used. And anyone that hacks a database to steal email addresses knows to remove it as well, to cover their tracks.