Codeigniter installation in subdirectory

your on Linux I think

,so another approach which i use for sub directory inside main web root of web server directory is via virtualhosts.

In that case you don't have to mess with .htaccess

use of virtualhost config also allows for easy production of access_log and error_log from CI4 in sub directory.

Basically then for live is a similar approach

CMS CI4 A CMS system, runs out of the box written on top of CI4

Arch Book  CodeIgniter4 on Apache(pages 92-114) 

CI4-CMS Github