I'm particularly interested in how you do about understanding the problem in more details, brainstorming solutions, working with your peers and getting feedback/review, and finally what the final set of deliverables are.
large companies is mostly a fiction, they are built from projects and teams where most of the design work is done at the team level or a bit more.
Defining Design processes is a well trodden path for agencies.
In 20+ years, I’ve not seen a huge divergence from; discover, ideate, refine, launch.
I'm not sure what it's like at super large companies, but I agree with another comment that assumes they make decisions based on micro-testing interactions with their millions of users.
At a mid-size company I worked at, we looked at metrics using analytics software (like Pendo and Full Story, not GA) and then AB tested variations to see if they moved users to our desired behavior.