How to remove mkcert SSL(mkcert development certificate), install Let's Encrypt SSL Certificate

[AngeloZou]

Description
I installed magento 2.4.6 on vps (ubuntu 22.04).
I installed SSL (mkcert development certificate) through the official tutorial, but the website cannot use ssl normally. How can I remove mkcert development certificate and install Let's Encrypt SSL Certificate.

Steps To Reproduce

bin/setup-ssl
bin/setup-ssl-ca
Expected Result
The frontend SSL is valid
or
Install Let's Encrypt SSL Certificate.

Actual Result
The frontend SSL is invalid
Not secure https:/ /www.123456.com
Your connection to this site is not secure
Certificate is not valid
Chrome error page detail:

I have tried the methods but still need help solving this problem.
#942