It was pretty informal, with HR asking some really basic questions, and then a couple of interviewers asking about my resume and experience. There was also a coding exercise, where I used Visual Studio to code up an exercise with an interviewer watching.
I received an offer, but the process was very unusual. There was no negotiation, and even terms discussed explicitly in the interview (like "flexible start date") were completely false. As this was during the covid-19 pandemic, I asked to move more slowly, but they continually pushed me for a rapid start date, contrary to their word. I asked questions about what to expect (regarding training, social distancing, and family health concerns), but received no answers. Communication was very poor. In the end, I saw many red flags throughout the process.