The same way you share them now: sharing the account name and password and doing whatever you currently do to deal with any 2FA they occasionally toss in.

If they also allow passkeys as an alternative form of login that doesn't need 2FA you can use those to make the account sharing more secure.

When setting up sharing with someone first change the password to something else, and then share the account name and password. After they log in the can add a passkey to the account on their device or devices.

Then you can change the password back to your real password. When they want to use the account they login with their passkey.

If the service doesn't accept login passkeys but does allows passkeys for 2FA, you have to use real password sharing, but at least they can have a passkey for 2FA which may be easier than how you know handle 2FA.

How do people handle 2FA with account sharing? If the site uses TOTP you can give them the QR code that you received back when you made the account (you do save a screenshot of such QR codes for backup, right?).

But how do you handle SMS 2FA, which seems to be far more commonly offered than TOTP?

For email 2FA I suppose you could set up a filter on your incoming mail that forwards any incoming code emails to the people you shared with, and hope that the time limit on the code is long enough for this to work.