Force use of SCA + Direct Payments when $disable_multivendor_checkout == ‘yes’

I use Stripe Direct Payments.

In the default WCFM Marketplace configuration this disables SCA because SCA cannot be used for a basket that contains items from multiple vendors.

but I have “$disable_multivendor_checkout == ‘yes'”

How do I force WCFM to use SCA when I have a single vendor basket and I am using Direct Payments?

I know several other multi-site operators who have this problem. Dokan does not have a solution so if you tell me how to do it I will publish it widely.