Context: I'm in the middle of adding Apple Log support to my photo/video processing app.
The iPhone has incredible video quality, but you're right that the default Camera app botches it (or requires you to shoot ProRes HQ which is objectively overkill). I've been using Blackmagic Camera to shoot 4K Apple Log into a 10bit HEVC file, and it works really well. The files are easy to grade, and the bitrate is enough for everyday use. Footage from the Blackmagic app is clean, clear and not over sharpened. I really hope Apple adds an HEVC Log option!
The iPhone has incredible video quality, but you're right that the default Camera app botches it (or requires you to shoot ProRes HQ which is objectively overkill). I've been using Blackmagic Camera to shoot 4K Apple Log into a 10bit HEVC file, and it works really well. The files are easy to grade, and the bitrate is enough for everyday use. Footage from the Blackmagic app is clean, clear and not over sharpened. I really hope Apple adds an HEVC Log option!