I only ever have to log back in on a device I was logged into if I delete all my cookies or have not logged in on that device in a long time. You're not deleting your cookies, are you?

Google hates you.

They hate most people, really.

I don't want to be that guy, but you should think about ditching google, a password manager can easily replace this "just use your gmail account so we can track you and you are locked in forever"

Technically, you're not allowed to have multiple Google accounts from their perspective. So the tooling isn't setup for it. You're probably also looking like a bot to them.

I'd suggest using the profile feature in Firefox so you can configure different contexts based on your needs such as a personal, uni and spam profile.

They also sell a hardware authentication device that might help simplify matters. It's called a Titan Security Key. You would need to research it to find out if it'll support being bound to multiple accounts.

Sounds like Google doesn't create per-account cookies and uses one cookie set per browser instance, so you're either logged in or you're logged out, one account at a time.

Browser containers or profiles might be the answer to what you need.

I've been using different Firefox profiles to run accounts in parallel for well over a decade at this point. Containers might be able to do the same thing, but on account of the aforementioned, I've stuck with the old way of doing things.

I don't have this issue. It sounds like Larry Page and Sergey Brin just don't like you

Idk man I don't work at Google

I don't know, I cut those fuckers out of my life.