It’s not a problem, you don’t need to make reservations for the MDR. There have been a bazillion posts on this topic on CC since the Welcome Back cruises last summer. All posts by cruisers in real time since last summer, including our experience in March this year on a TA, have said you can be seated in the MDR whenever you want. Earlier tends to be best, sometimes a bit later you might have to wait a few minutes, but every cruise is different on when people like to eat. No worries. (The TA in March was our fifth Viking cruise, and the first since Covid.)