How do you brainstorm tricky stuff with your remote teammates?

Depends on the topic and the size of the audience. If it's a bigger team, it's useful if everyone can write down their thoughts before a common get-together, and then ideate in a video call, preferably using some collaboration tools, like Miro.

We do a monthly design thinking/ divergent thought session called "Unlock" and invite all of our teammates (optional) and run activities that are designed to stimulate big thinking... as inputs for later more convergent work.