This page lists all of the places to ask for help or discuss Javalin, in no particular order.
The GitHub repo (https://github.com/tipsy/javalin) is where most of the action happens. You can create issues to make feature request, to report bugs, or to ask questions.
Discord is the primary chat server for Javalin. You can use this invite link to join: https://discord.com/invite/sgak4e5NKv.
Javalin doesn't tweet a lot, but it does retweet and like Javalin related things: https://twitter.com/javalin_io
The gitter chat server isn't very active, but it does have a lot of idling members: https://gitter.im/javalin-io/general
Javalin has its own tag on Stack Overflow, but it's not a common place to seek help: https://stackoverflow.com/questions/tagged/javalin