Since posting the dmesg from my Pinephone running OpenBSD 7.0, I've received a number of emails off-list asking similar questions, such as how to compile U-boot, how build the install media, how to flash the internal eMMC, etc, etc.
I've put notes about the steps that I followed up at: https://www.exoticsilicon.com/crystal/pinephone_openbsd However, this is intentionally not a step by step guide. Be aware that the system is far from usable at the moment, so unless you are interested in debugging the issues, you'll not see much more than the dmesg that I already posted.
