I have used Bulma and UIKit. Bulma is a light CSS based framework that can be easily customized. UIKit is full-blown with tons of JS features but I find it hard to customize.

Thanks. I have opened a ticket.

UPDATE - They did reply but no help. Paddle does support debit cards but it should not be 3D secure/OTP protected. And this is not the case with most of the people here.

Paddle looks good. Very customizable, supports multiple currencies, and a good SDK. But I created my payment page and tried to pay with a debit card and it didn't work. Obviously, I was trying to sell a product and not a recurring payment type service. So do you know how I can fix this?

Thanks in advance. I really appreciate your help.

on the phone?

You can outsource it from low cost countries like India (where $25 is like too much IMO). I know some students who are excellent devs and who would like to earn some quick bucks. Ping me if you are interested.

Got a donation for my software Clipjump ($10) in 2013.

Thanks for your answer. It helps me realize that I should be able to ship my own backend quite quickly. I don't have prior Firebase experience, and though it was made to save time, that time saved would be ineffective in my case since I would have to do a lot of googling.

That's a good idea. I will give it a try.

Many folks including Nomad List are using Mapbox for powering their maps. www.mapbox.com/

+1 for this idea. We can even have a feature to list/filter through todos and complete them.