Google App Maker Alternatives: free, simple, beginner-friendly, secure

I need to build a secure commercial web application that guides users through steps (like, 1, create your account and login 2, select subscription type, 3, redirect to payment page, 4, other). Some of these steps involve making backend HTTP GET/PUT/POST requests based on the user inputted information (so perhaps Wordpress, Wix, Weebly, Squarespace, and some others may be ruled out). I could also use PythonAnywhere or Google Cloud App Engine but it requires much more configuration. I have also tried MS Azure which had a perfect one-click enable login setting but it was expensive. I have also not given Zoho Creator a try since it is not free.

I noticed that Google App Maker was released in beta for GSuite users, which is excellent because it is Google, is secure, free, and allows for super simple web development. But since it is still in Beta they have blocked off sharing web apps outside of your own organization. I looked around and I found Firebase (requires some coding to implement the login, no WYSIWYG editor) and Google Apps Script (does not have a WYSIWYG editor and shows yellow bar at the top, but login is automatic), which I will end up using unless you can provide any great alternative.

Am I missing any affordable/free, simple, beginner-friendly, secure web development platforms?