Go to a bar

Depending on your state's coronavirus restrictions, this may still be possible. However, in most places, they won't serve drinks past 10 p.m., or let you drink without buying food. So, just don't go out the night before you turn 21 and expect to be able to drink.

Go out to dinner

Although, this way, you can't take a shot the moment you turn 21, you'll still get to go out and drink for your 21st birthday, and get much better food than you would get at a bar.

Go out to brunch

Slightly earlier than going out to dinner, you get to get drunk early in the morning on your 21st, along with eating a delicious breakfast meal.

Host a get-together

Inviting over a few friends (however many the state or county allows) can still be so much fun for a 21st birthday. You can do everything you'd do with your friends at a big party, but, this way, you cut out all the people who you probably would have ignored anyway.

Go alcohol shopping

You can bring a few friends to a nearby liquor shop and just buy anything you want, since you couldn't do that in the past. And, if you look young enough, they might even not believe your ID is real.

Do a free things day

Since so many places offer you free things on you birthday, why not make the whole day dedicated to getting them all? To make it 21st-themed, you could go with a few friends and have a car full of alcohol that you guys can drink (while the person who's still 20 drives.)