What is Strong Customer Authentication (SCA)?
PayPal checkout is now SCA compliant. No further action is necessary.
Stripe Checkout is now SCA compliant for both one time and recurring payments.
Below is a zip file of Leaky Paywall with the SCA updates. Please delete your current Leaky Paywall plugin and install this one instead.
Once you've installed and activated it, go to Leaky Paywall > Settings > Payments and select Stripe Checkout. That will use the new Stripe hosted checkout page that is SCA compliant.
Note the registration form checkout method is still in development for SCA compliance.