Does it take two to administer the sacrament?
This is a common question that has only a partial answer, I’m afraid.
As far as the actual blessing of the bread and water, we have the following guidance on the administering of the Sacrament.
After the hymn, the person blessing the bread kneels and says the sacrament prayer for the bread (see Doctrine and Covenants 20:77).
The bishop makes sure the sacrament prayers are spoken clearly, accurately, and with dignity. If someone makes an error in the wording and corrects himself, no further correction is needed. If the person does not correct his error, the bishop kindly asks him to repeat the prayer. The bishop uses discretion when asking for the prayer to be repeated. He ensures that doing so does not cause undue embarrassment or detract from the ordinance. Another person at the sacrament table can help as needed.
After the prayer, priesthood holders reverently pass the bread to the members. The presiding leader receives it first, after which there is no set order. Once a tray is handed to members, they may pass it to one another. — General Handbook 18.9; Para 4-6
Similar instructions are given for the water.
The language of these instructions are such that it can be done by one person who holds the proper priesthood authority to do so. In other places in the Handbook, it is clarified that the Bishop, who holds the keys of the Aaronic Priesthood, must authorize the actual ordinance being performed.
In answer to your question, it does not state that two priesthood holders are required to properly administer it. So, it appears that only one Priest or Elder is required to administer the Sacrament.
Likewise, the COVID quarantine has provided us an interesting look into just how far it can be taken. I’ve known of men today who live on their own and are permitted to bless and administer it to themselves as lone individuals.