Ooypunk

I solved it, this did the trick:

add_filter(‘locale’, function(){return WPLANG;}, 100);

I was afraid you were going to say that.

Well, thanks anyway. ??

Not very: the 4 newest. I do that now by sorting: post_date => DESC.

Thanks for the link. It pointed me in the right direction, I think.
I couldn’t find the database tables mentioned in that page, so I tried setting up again to see when they should be added to the database. That didn’t happen (without any error notice(!)) and I got the loop again. Then I checked the privileges of the database user and found that the user didn’t have the create privileges. I gave it all privileges and then they got added and the loop was gone!

Thanks for the help!

No. I didn’t know that was necessary?
What part should be deleted?

Thanks, Ipstenu.

I tried again and indeed, now that notice came up. I changed both the ‘WordPress address’ and ‘Site address’ (not sure which one you meant) and the notice didn’t appear again.
But after that the problem itself (the loop) appeared again.

Update:
I tried looking into the code and found out the redirect happens in ms-settings.php on line 94. After seeing that, I tried adding the NOBLOGREDIRECT define to the config, like this:
define( 'NOBLOGREDIRECT', 'https://www.mydomain.net' );(domain is the same as defined in the Apache VirtualHost)

This did one thing: instead of redirecting to https://www.mydomain.net/wp-signup.php?new=www.mydomain.net, it redirects to https://www.mydomain.net itself. But it still keeps looping.
I don’t understand: if WP wants to redirect me to the login-page, why does it try to redirect to wp-signup, instead of wp-login? Something I forgot to install, or didn’t configure properly?