This issue comes up regularly, and is confusing for this reason:
The General Instructions of the Roman Missal (GIRM) assume a single chalice and ciborium in the instructions.
If it were the case that the parish is small; and only the priest is needed to distribute the the Body of Christ, than the Deacon is the one to distribute the (singular) chalice of the Blood of Christ.
Hardly any parishes are actually that small, and use that few ministers to distribute Holy Communion.
During COVID-19, most (if not, all) parishes have suspended distribution under Both Kinds. As a result, the Deacon should distribute the Body of Christ, alongside the Priest.
An Ordinary Minister of Holy Communion is always used before an Extraordinary one. If there were multiple locations distributing the consecrated Hosts, and multiple locations distributing the Precious Blood, the Deacon would typically take the Chalice next to the Priest.
He may, however, also take the position next to the Priest in distributing the consecrated Hosts. There is nothing wrong with this.
This is very common at weddings and funerals; the Priest and Deacon typically take the center positions as they are better equipped to handle the confusion of people coming up that aren’t Catholic, want a blessing instead, etc.
Some parishes add extra distribution places simply to create a need for more EMHC. This is just silly.
All Ordinary ministers, unless impeded (for example, difficulty standing, or trouble going up and down the sanctuary stairs), should distribute Holy Communion before the need of EMHC are employed.
If there are only one ciborium and one chalice, yes, the Deacon should take the chalice. But, in any other arrangement, it is appropriate for him to distribute either species.
Deacon Christopher