As always, let me start saying your work is amazing and beautiful. Congrats!
I'm having some problems showing my Posts Page in other languages than the original. I set the Front Page and the Posts Page to be a Static Page. This can be done in Options > Reading.
I have no problems showing the Front Page in the correct language. In other words, the following is working:
mysite.com --> Front Page (front-page.php) with default language
mysite.com/en --> Front Page with other language than the default
However, I set my Posts Page to be my page named "Blog". This title is by chance exactly the same in the other languages. When I navigate to my posts page when in my default language it's working correctly but when I navigate to my posts page when in other languages than the default it prints de Front Page.
mysite.com/blog --> Posts Page (home.php) with default language (works!)
mysite.com/en/blog --> It prints de Front Page in the other language (in this example, english)
I also experience some trouble with the 404 Error Page (404.php). It always show the 404 Error Page with the default language locales.
mysite.com/a-random-non-existent-page --> it shows 404 in the default language
mysite.com/en/a-random-non-existent-page --> it shows 404 in the default language (wrong!)
Am I doing something wrong? Am I forgetting something? This is due to something or to some feature not already added to the plugin?
Thank you a lot for your help!