In addition to the accepted answer (the project is on Flutter but it's basically the same as native):
I do have folders Base.lproj, en.lproj, xx.kproj. etc. with InfoPlist.strings in each.
This file has lines like this (no quotes around the key and with a semicolon at the end):
NSLocationWhenInUseUsageDescription = "My explanation why I need this";
Check that you have your languages in your YourProject > Info:

Also, check the project.pbxproj file, it is in XXX.xcodeproj/project.pbxproj:
it should have all your languages in codes (en, fr, etc.)

But even then it didn't work. Finally, I noticed the CFBundleLocalizations key in the Info.plist file. (to open it as raw key-values in XCode - right mouse button on the Info.plist file -> Open As -> Source Code)
Make sure that the values in array are codes rather than complete words, for example fr instead of French etc.
<key>CFBundleLocalizations</key>
<array>
    <string>en</string>
    <string>ru</string>
    <string>lv</string>
</array>
And double-check that your device is set to the language you're testing. Cheers
P.S. "Development Language" doesn't affect your issue, don't bother changing it.