I interviewed for a senior front end position in the last year, from what I understand it's very team dependent. My initial phone screen was with a mid level member of the team I was applying for. They had a basic html page that they had me add css and plain javascript to, adding some interactions and message display. Really testing the basics.

Yeah, OP I'd ask who your interviewer is because it might dictate how that first interview goes. If it's with another engineer on the team, it'll probably be a lot of technical interviewing and then some behavioral questions. If it's with the hiring manager, it might lean more behavioral