I'm happy to report that today Chase resolved my disputed easyJet charge in my favor. I submitted it on April 8. Either the time passed with no objection from easyJet, or easyJet expressly consented to the chargeback.

I continue to recommend disputing these charges with airlines when they cancel your flights. First, request a refund. Alas, some airlines are making that a challenge. If that's not an option on the website, send an email to customer service. Wait seven days (the EU deadline for refund). If no refund, dispute the charge with your credit card issuer.