SOLVED: iPhone media exported from Premiere is way overexposed in H.264

If your HLG clips are over-exposed on export it is because your color management settings are not correct.

HLG clips, HLG sequence, and export preset selected from those with HLG in the preset name ... good.

Any one of those not matching, fail.

For Rec.709/SDR export, any HLG clips must be set to Rec.709 with the Override-to option in the Modify/Interpret Footage dialog, the sequence must be Rec.709, and export presets that do NOT have HLG or PQ in the preset name  ... good.

in the future, to find the best place to post your message, use the list here, https://community.adobe.com/

p.s. i don't think the adobe website, and forums in particular, are easy to navigate, so don't spend a lot of time searching that forum list. do your best and we'll move the post if it helps you get responses.

<"moved from using the community">

I mean choose the PRESET "Match Preview Settings" - it's a preset not a format. Format will automatically populate as Quicktime.