The GitLab interview process is described in the company's handbook (it's public, go read it!). The description is accurate and will evolve to reflect any changes that happen over time so read that if you want to know what the process is like.
Everyone was super nice in the entire process and interviewing remotely from the comfort of your home (or whatever other place you choose) makes it feel more like a fun conversation about work rather than an interview.
My interview process did take a bit more time than what is described in the handbook, however the Security Director at the time (Kathy Wang) was leaving the company and that most likely added some delays. I'm quite sure that in a more "normal" context the process would have been a bit shorter. There was about 3 weeks between the screening call and the offer (includes a few interviews and a background check).