So what would you propose as a solution?
I suspect they will have to just implement every possible measure to try and keep demand suppressed - like encouraging people to go by car where possible (perhaps with measures like reducing parking restrictions), continuing the drive to get people to work from home where practicable, keeping the least important businesses closed, spreading demand, et cetera. Then on the supply side monitoring loadings and adjusting timetables and diagrams to provide extra capacity at the times when it's needed. Perhaps marking certain seats out of use in order to get people to spread out in the most efficient manner possible would also help a bit.
How one makes this work on some of the inner suburban routes like London Overground, or the Underground, goodness knows to be honest. Even now there's parts of the Underground that are packed at certain specific times of day.
On top of this as I said elsewhere I think masks would have to be compulsory as an added measure.
The TOCs will also need to max out on train lengths where possible, especially at times where they might not normally need to like early morning, peak shoulders and afternoons. The fixed-formation nature of the 700s may prove an issue due to the inherent inflexibility of the 8-car units. Unfortunately extra services will almost certainly be out of the question due to lack of drivers, so it's going to be a case of shuffling things to make the best use of what's available - although just taking GN as an example I struggle to see what shuffling will actually be feasible by the time things like platform lengths are taken into account.
Taking myself as an example, I could go by car if I need to, although generally I *prefer* not to. I'm fortunate in having a choice of free car parks I can use, and I can do the journey in essentially the same time except at the busiest times. Generally I don't travel at busy times so most of this probably won't be an issue for me, fortunately.