As others suggested, you can post in médium or other websites.
Yes Medium is also a great platform for the publisher and have lot of features keeping in mind you follow their
guidelines and ofcourse it's free and if you want unlimited access and more features unlocked you can pay $5 fees to access lot more.
But as a content writer it's really a good platform and he can choose this option in crypto category and follow other publishers as well.
But why don't you post them here? If they are really good and bitcoin focused, you can even monetize them here by joining signature campaigns.
That's also a good option and he can learn as well through this forum.If he help newbies and forum members through his threads he can get merits and rank up as well and have benefits from it as well.