Just head to the list, find the make of your Chromebook or the one you're looking to buy or pass along. Google maintains a full list of AUE dates for all models. Getting the AUE date for any Chromebook is as simple as finding its name on a list. Last year's Lenovo Chromebook Duet has an AUE date of June 2028.
The good news is, Google makes it extremely easy to find out the date for any Chromebook.
That's a good long time for a new Chromebook, but things are trickier when buying an older or second-hand model. The Samsung Galaxy Chromebook 2, for example, was released this March and has an AUE of June 2028.