Enable access to a single directory

You can either create a skip/bypass rule in your root .htaccess file to not have this directory checked or you can add a RewriteEngine Off .htaccess file in that directory.

directory skip/bypass rule
https://www.ait-pro.com/aitpro-blog/2252/bulletproof-security-plugin-support/checking-plugin-compatibility-with-bps-plugin-testing-to-do-list/#Custom-PHP-Applications-Outside-WordPress

RewriteEngine Off .htaccess file
https://forum.ait-pro.com/forums/topic/rewriteengine-off-htaccess-file/

Did this solve the issue/problem? If so, please resolve this Thread. Thanks.

Yes, it did, thank you.