Answer

I had a column about this (following Rabbi Amsalem). Is it currently forbidden to go to the mikveh? I haven’t heard that it is.
Even if it is, I don’t think there is room to permit it in a situation of a lockdown that is limited in time. It is proper to restrain yourselves. Only where people will not be able to hold out, then there are opinions and situations that lessen the prohibition (let him go to a distant place and do as he wishes). And even that is not in the shower, but in a mikveh made of drawn water.