How to implement subdomains through folders in wordpress?

Question

WordPress

Task: make regions for the information site through folders in the URL (note: site.ru - domain, site.ru/msk - region).

Of the solutions, multisite is the first to be pushed to the head, but multisite will create tables in the database for each region. If you need to change a post, you will have to change it for each site. Okay, there is a plugin for clones. But there is contact form 7 which is not cloned. And then there are a lot of problems with editing content in all regions, including the main domain.
Bottom line: multisite is not an option.

I would like a simple solution, as if I were doing it through 3rd level domains. You create a table for the regions, write a class for pulling up information on the region (contacts, phone numbers, addresses, meta tags) and insert the variable into the template.

Ideally, I have one table in the database with regions and info on them. A class for determining the current region and returning information about it in a variable.

Question, actually: how to implement it? Intervene in the router and change the url?

I do not need a ready-made implementation, I just want to understand in which direction to think. Thank you!