Rules for using 2d10 instead of 1d20 for DD Next

Regular roll

Roll 2d10 and add the result of the two dice. If the sum is greater than the target number, then it is a success. Otherwise, it is a failure.
If the two dice are equal and your roll is a success, then it is a critical success.
If the two dice are equal and your roll is a failure, then it is a critical failure.

Advantage

Roll 3d10 and take the two dice that have the highest value.
Add the result of those two dice. If the sum is greater than the target number, then it is a success. Otherwise, it is a failure.
If the two dice are equal and your roll is a success, then it is a critical success.
If your roll is a failure and the three rolled dice are equal then it is a critical failure. Otherwise it is a regular failure (even if the two chosen dice are pair).

Disadvantage

Roll 3d10 and take the two dice that have the lowest value.
Add the result of those two dice. If the sum is greater than the target number, then it is a success. Otherwise, it is a failure.
If the two dice are equal and your roll is a failure, then it is a critical failure.
If your roll is a success and the three rolled dice are equal, then it is a critical success. Otherwise it is a regular success (even if the two chosen dice are pair).

Statistics

You can find a statistical comparison between 2d10 and d20 following this link

Notes

You take the dice that have the highest value, not the dice that is the best for you. This mean that if you roll [5, 5, 7] and have to score 10, you take [5, 7] and not [5, 5]. Otherwise you would have a too high critical success ratio (if you have to score 5 and more, nearly 1/4 of the rolls would be critical hits).

Also, you have a critical failure only if the three rolled dice are equals. As for the critical successes, this rule prevent a too high critical failure ratio.

Sames remarks applies for disadvantage.