I’m currently using b2evolution under a single domain (APKNite) to host multiple blogs in different subfolders.

Do you mean you have multiple blogs or multiple collections in one installation?
Do you mean you have multiple installations, like one in each subfolder?

I want to reinstall it so that I can have a single installation across multiple domains/subdomains/subfolders.

So you want one installation that uses the same database for multiple, collections where each collection is accessed via a different domain/subdomain/subfolder.
If this is the case I don't see you need to mess with apache as any domain or subfolder can be directed to any collection purely by url.

Something I don't understand maybe ??

My question then is if there is a way to do this under a shared hosting plan?

Yes, absolutely: https://b2evolution.net/man/multiple-domains