So, it appears that using the hashtags science and technology gets you posted on stemgeeks.
Which makes sense considering their topic, stem.

If you see value in acquiring more stem tokens, then you can post through their interface and earn more, iirc.
Your posts will still appear on your feed when posting through stemgeek's interface, so don't repeat them.

You will also earn stem tokens by powering them up and voting with them.
You can do this powering up in the peakd wallet.