Custom login for Apache Superset?

Question

I'm running Apache Superset 1.4.1 on a Debian server.

I am attempting it on Ubuntu 20.04 VMs behind a proxy. And I am running superset on http://localhost:9000/(in dev mode)

How to reproduce the bug

1 Clone Superset repository

2 cd superset

3 docker-compose up

4 in another terminal(cd superset/superset-frontend)

5 npm run dev-server

Superset Supported Authentication Types:

Database,
Open ID
LDAP
REMOTE_USER
OAUTH 

The user wants custom login with image captcha. So where do I make changes to create a custom login? I suspect this would be handled on the Flask side of things but I am unable to find any help on how to approach this challenge.

I am a Flask novice so any pointers will be very helpful.

Thanks!