Dealing with static linkage is a giant pita because you have to provide all the object files for your code basically. I don’t think anyone really bothers with statically linking LGPL Qt into a non-OSS executable.
It's not hard at all. You can add them to some directory with your app, or they can be behind some url, or you can mail them physically in a USB stick to anyone who requests them by mail or phone.
You just have to be able to provide them if somebody wants them. In reality nobody ever wants them. It's just some directory with gpl-stuff/ you add to your software.
How hard it is to have some binaries lying around?
You mentioned LTO. Don't the LLVM and GCC LTO implementations currently involve outputting compiler IR to object files, then running the optimization passes against the full collection of object files prior to linking? So they inherently collect all the object files together in a linkable form.
(Of course, it's probably more efficient to just dynamically link Qt and pay for a license if you want to publish for iOS.)