I skipped the OA and was directly contacted for a coding interview. It was quite dry. They didn't ask any behavioral questions and jumped straight into coding. The coding question itself was super easy - a simple stack problem of keeping track of parantheses. The extension asked to make a visual editor (so it was a bit more OOP) and simply remember the positions of the parantheses from the previous subtask and do some string manipulations depending on if you encountered a paranthesis there.

Collaborative problem solving, not like leetcode style. For of system designing and low level programming: visual machine, compilers. There is no special needs to prepare, just be familiar with the language chosen and think aloud.