If you've tried to contact a national forest office lately about getting a wilderness permit for this summer, you've found that things are pretty darn confusing. First of all, all of the offices are closed to public traffic due to the COVID19 pandemic. Fair enough.
But the websites and information coming from these offices is also quite confusing. Some offices and some national forests are issuing wilderness permits, either via an on-line system like recreation.gov or via telephone, fax or email processes. And the same is true for our national parks.
Others are not issuing permits at all, but only opening hiking trails for day hikes.
Some forests are asking you to recreate locally (a suggested response to COVID19) and not drive to visit their region at all.
And as far as we can tell, while no USFS campgrounds are open, dispersed camping is allowed in many of the forests, but not all of them. It looks like Lassen National Park has opened its campgrounds, but it may be the only one. And some USFS forest offices are closed completely--not answering the phone, not offering to return any left messages.
We'd love to give you some advice as to how to proceed, but it also appears that the situation and the responses to it from the various National Forests are constantly changing. All we can suggest is that you call each office individually (numbers are available from the USFS websites) and ask what would work for them, and find out what would work for you.
If you feel that backpacking is a safe activity both for you and for those with whom you might come in contact, you can find regions where that is possible.
Just think of the search as part of the adventure.