Do any mainstream phones ship with a headphone jack now?

The latest 7nm phone from Huawei lets you choose between using the second sim card tray for a sim card or removable storage up to 256GB (albeit their proprietary storage medium). From my experience, plenty of Chinese phones offer what geeks in the US want (expandable storage and removable batteries).

https://en.wikipedia.org/wiki/Huawei_Mate_60

Removable storage NM card 256GB

SIM

Card slot 1: NANO-SIM

Card slot 2: Choose one of the two NANO-SIM or NM memory card"

Motorola has been consistently producing Androids with SD card slots. Heck, they still even have headphone jacks.

Though AFAIK, it's only on the Moto G family, which isn't a flagship series, so it won't be as capable as a Galaxy, Pixel, or iPhone.

There's plenty of options on the market for phones with headphone jacks. You won't find an apple or samsung flagship with one because it directly impedes waterproofing and isn't desired by the vast majority of people buying those devices. It's common to see on low and midrange phones.