1 Set up your repository

Create a public repository named pages to make the site available at the main subdomain.

Create a branch pages in a repository:
git switch --orphan pages
git rm --cached -r .

2 Upload your files

Push your static content, HTML, style, fonts, images or anything else.

3 You're done!

Access your new website using this link:
https://USERNAME.freecumextremist.finance[/REPOSITORY][/@BRANCH]

To use a custom domain, create a file .domains in your repository with the domain name to use.

Then, add a DNS record to that domains:
CNAME [[branch.]repo.]user.freecumextremist.finance

Or for zone roots where CNAME doesn't work:
ALIAS freecumextremist.finance
TXT [[branch.]repo.]user.freecumextremist.finance

If ALIAS isn't supported, use A & AAAA instead:
A 158.101.113.160
AAAA 2603:c020:4004:62ee:abcd:1234:0:a
+ TXT as above