I've managed (thank you FT8!) to have LOTW-confirmed contacts with the 6 applicable continents.
However, on reading the ARRL page for the WAC award it says that you have to apply on paper and that LOTW contacts do not count but contacts in your DXCC account do count.
Could I get the WAC award by filing an online application in LOTW to get my LOTW contacts credited to my DXCC account and then file the paper WAC application and check the box saying the listed calls are in my DXCC account? Or is there no way around needing paper QSL cards to claim the ARRL WAC?
And speaking of the LOTW DXCC application, can you only file it when you've actually gotten 100 DXCC entities? Or can you file the application at any time to get credits put into your DXCC account even if you haven't achieved any DXCC award yet? The LOTW site doesn't make any of this clear.
Update: I was able to successfully submit a DXCC application to claim the LOTW credits for my DXCC account even though I have less than what's needed for the base DXCC award. (You still get charged for the DXCC certificate you won't be getting for the application.)
After doing that I've mailed in the paper WAC application. We'll see what happens and I'll try to remember to update this question with the result.
Final Update: Received my WAC certificate today. So that’s pretty empirical confirmation that you can get WAC without any paper cards at all. Get your necessary confirmations in LOTW, then get those credited to your DXCC account, then file the paper WAC form referencing the QSOs in your DXCC account.