The Pine store has official cases:

Tight-fit cases of other phones can’t be used with the PinePhone because most times the proportions and/or camera notch won’t fit. The phone can however be used with most "phone sleeves", such as those from fitBAG. The sleeve from fitBAG for the Xiaomi Redmi Note 8 Pro fits the PinePhone tightly.

The OtterBox uniVERSE Case for Samsung Galaxy XCover Pro is reported to fit the PinePhone well without much modification.

The following accessory is made by the community: