Following is from Rav Hershel Schachter, via YUTorah. You can find the whole thing, including the Hebrew with the Ma’areh Mekomos, if you go to that site and look for “Piskei Corona 14”. I tried copying the Hebrew over, but the formatting got messed up, so I only copied the English.
an Israeli Yid
Ten men who are standing on different porches cannot be joined together in order to constitute a
minyan even though they can all see each other. In order to constitute a minyan for Devarim
She’bekedusah (like Kaddish and Kedushah), the ten men must all be standing in the same room. (It
should be noted that in smaller spaces, such as a shiva ho
use, care should be taken to make sure that ten
men are davening together in the same room. If less than ten are davening in one room and less than ten
in an adjacent room, even though they can clearly see one another, this would not constitute a minyan.
In order to create a minyan there must be ten participants davening in the same room.)
It should certainly be discouraged for people to make a minyan outside on the lawn even if they maintain
the minimum distance recommended by the health department. One should not place himself even
into a situation of a doubtful sakanah in order to daven with a minyan.