Just found out I passed the coding interview phase. Next step is a "live" (covid adapted) whiteboard interview.

I haven't had to do one of these before. Anyone have any advice on these?

If you know what platform will be used for the whiteboard interview (e.g. Miro, Diagrams.net, LucidChart, ...) then make sure you're comfortable enough with it to use it without any issues (under pressure).
If you don't then perhaps ask them what they plan on using.

Other than that I'll suggest to practise on Miro (or even a real whiteboard if you have access to one) and making sure you speak about what you're thinking, like going through the problem, possible solutions and what goes through your mind as you solve a problem (e.g. some LeetCode problem).