How can I best adapt my seminar slides for a virtual presentation?
There is nothing more boring that watching static slide after static slide while listening to someone who you can't see. If at all possible, come up with a system where for the most part, people see you via video chat, and if you have something that absolutely needs a slide -- a picture, a formula -- switch to screen sharing.

This kind of system requires you to think carefully about what actually needs to be on a slide. Minimize the amount of text, maybe to zero on many of the slides you would ordinarily have (and then skip those), so that your audience doesn't actually need the slides. This way they also get to pay attention to you.

All of this is of course good practice anyway: Packed slides often lead to people reading ahead of what you have to say and not paying attention to what you actually say. The best talks are those with minimal text that serves to abstract and highlight what you say, but not distract. This is your chance to practice this!