Is ‘OK Boomer’ an example of casual ageism? If yes, what other examples are there?

While “OK boomer” is a mild insult, whether it’s ageist or not depends on the situation. If someone uses this phrase one time only and to joke around, they’re not necessarily trying to discriminate against your age. However, if someone tries to shut down an argument by bringing up your age, it’s 100% ageism.
Other ageist phrases can include: “You don’t look {insert age}.” “If you have trouble using this technology…” “You have a smartphone?!” “Seasoned” “You’re still working?” “Past your prime” “You still have time.” “You can’t teach an old dog new tricks.”