2020 is pretty straight forward: you claim the child for full tax benefits. If the mother files a competing return, the IRS will handle the dispute*.
2021 (odd number year) will be more interesting, but apparently you may have that resolved by a new court order.
*If someone else claimed your child inappropriately, and if they file first, your return will be rejected if e-filed. You would then need to file a return on paper, claiming the child as appropriate. The IRS will process your return and send you your refund, in the normal time. Shortly (up to a year) thereafter, you'll receive a letter from the IRS, stating that your child was claimed on another return. It will tell you that if you made a mistake to file an amended return and if you didn't make a mistake to do nothing. The other party will get the same letter you did. If one of you doesn't file an amended return, unclaiming the child, the next letter, from the IRS, will require you to provide proof. Be sure to reply in a timely manner. You will have to prove the child lived with you.
Winner gets the tax benefits; loser gets to pay the IRS back with penalties and interest. The custodial parent almost always wins. The IRS goes by physical custody, not legal custody.
