Great article on 520 Errors by our sister site.

https://managingwp.io/2021/08/27/cloudflare-520-errors-explained-and-investigated/

If you ever had your site at a hosting provider that had a Cloudflare integration, and you decided to opt for your own Cloudflare account but had issues with SSL. This community post is related.

https://community.cloudflare.com/t/enabling-cloudflare-proxy-shows-invalid-ssl/375374