I served as national field director for the Bernie Write-In campaign in 2016 and he received (an all-time record) 575,000+ votes, good enough for sixth place in the general election.
There is no reason he cannot receive Write-In votes in 2020, operating under something called the 'without his consent/against his will' Theory. This will, in fact, work just fine in twelve states that guarantee to count every last single Bernie vote: Alabama; New Hampshire; Vermont; Rhode Island; Oregon; Wyoming; Washington state; Wisconsin; New Jersey; Iowa; Pennsylvania; and the District of Columbia (not a state, but they still vote). WOW: Two down votes, and one vote to delete. The truth hurts, doesn't it?