Out-of-the-box, no. With custom work, yes. The amount of effort is not large, and there are off-the-shelf solutions available. The name commonly used is "engagement timer."

By default, GA only sends one hit on page load. If there's no second hit, there's no way to tell if someone was looking at the page for a second or a minute or an hour.

How do they handle it? A keep-alive style ping, or something like a beforeunload event hook?

In theory the correct way to send analytics when leaving the page is via navigator.sendBeacon, although it's not clear how reliable it is: https://volument.com/blog/sendbeacon-is-broken (note: read the comments for some rebuttals to the article)

You get an idea how long someone has the page open yes.

But only if the user goes on to visit another page. You don't see how much time they spent on last page they visited, even if they only visit one page, by default.

Depends on the events you are tracking.