Do Apple Store locations allow walk ins for Genius Bar?

Some locations will handle walk-in problems, but not all of them allow for that. Unfortunately walk-in may also require you to wait for someone if there are appointments scheduled before you. Depend on how much wait time you have and if they support walk-ins.

Typically, you can walk in and join the waiting list. If enough appointments are 'no-shows' or if they have openings for the day, they will try their best to get you in.

In the busier stores, this can sometimes be an exercise in frustration as you watch one person after another walk in right at appointment time while you simmer in the waiting line.

So the short answer to your original question is 'yes, but...'

Best of luck!