The best way to reach me is via email. But it can take a few weeks until I reply. Unfortunately I'm always very busy. I know I have one unread email about Flarum at the moment, I have not been able to look at it yet.
I do try to reply to everyone, even if in some case it took months. If you don't hear back from me, feel free to re-send it, ideally in the same email thread, just to bump it.
I probably won't be able to take any freelance Flarum work this year. If Flarum 2.0 drops, I'll take some time aside from my other work to update my most important extensions, but that's probably the most I will be able to do.
If you have an issue with an extension, the best is to write in the extension discussion. I read the forum very regularly.
