Yes you can still use Stripe payments, however, it has changed and you will have to click a box in your Stripe account to make it work. The tick box is you agreeing to be fully liable legally and financially for the unencrypted untokenized credit card details that you are passing to them, and thus you are taking on the full force of the compliance regulations.
If you are setup to do this, or are happy to pay a lot of money to make it happen, it will work.
Both Paypal and Stripe give you options that allow you to send the user to put credit card details directly on their sites thus removing any handling of credit card information by you. Unfortunately the Unifi system has not been updated for a long time and I wouldn't hold my breath on it.
I have looked at combinations of pfsense, coovachilli, freeRadius, with openwrt firmware and openwisp for management, but this time round I am now too short of time. Maybe work towards the next one . . .