On the sustainability front:

WFH means people aren't commuting. This is good, as we use less energy, particularly gas in our cars. On the down side, public transit agencies may have to dramatically cut service, increasing people's reliance on cars to get around. At an extreme level, they may go bankrupt due to lack of ridership.

Energy - home energy use has increased home residential energy use by between 7% and 23%. Lower income residents who do not have air conditioning can also suffer disproportionately. Higher income workers can readily afford expensive home upgrades, like adding a home office. Since empty commercial buildings still need to be heated and cooled, the energy savings aren't as great.

Real Estate - the US will need to delete 18% of its commercial real estate, worth ~$1.5 trillion. This will leave every major city with a giant hole in its central city and cause major economic disruption in both the real estate investment market, construction I distry and walkability of cities. We may be staring down the barrel of another "white flight to the suburbs" that we saw empty out cities from the 1950s through the late 1990s.