Config
As you know the Bootstrap 4 or Bootstrap 5 is in Plugin (HTML-Head)
You have to create 2 files
- File 1 to Disable Bootstrap 4
include/config/CMS/Plugin/HTML-Head/config/Bootstrap4_PublicCDN.cfg.php (Disable)
- File 2 to Enable Bootstrap 5
include/config/CMS/Plugin/HTML-Head/config/Bootstrap5_PublicCDN.cfg.php (Enable)