But… Mine isn’t openwrt…
That’s fine. I just want to boot the R4.
Probably a discussion by itself, and one worth having imho:
In my experience SanDisk SD cards are fine – as long as what you buy turns out to be actually “made” by SanDisk (or at least intended by SanDisk to carry their logo…). Out of 10 times buying micro SD cards in major retail shops, I had more than half of them turn out to be fake (easy to identify using mmc-utils as vendor/product IDs don’t match). Chances of getting fakes turns out to be the highest for SanDisk and Kingston brands, probably because those are known and popular brands but selling different things made in different factories.
So general recommendation regarding microSD cards, no matter which brand: Buy them directly from the manufacturer and avoid any intermediates because they will fool you. I got so annoyed by seeing micro SD cards having problems before even written completely full for the first time, at some point I ordered a batch of super high end Samsung Pro EVO cards from samsung.com and those work fine now for a long time, total written data in the terrabytes for a 32 GiB card.
I had many cards flying around, Kingston, Sandisk, Toshiba, Transcend, … all of them have died in the meantime. One very cheap AData one seems to survive for a surprising high number of writes, but that can be a coincident 
tl;dr: Buy high-end cards directly from the company which makes them.
early beta of mainline OpenWrt image is here in case you want to try: http://downloads.openwrt.org/snapshots/targets/mediatek/filogic/openwrt-mediatek-filogic-bananapi_bpi-r4-sdcard.img.gz
Hey Daniel,
This sounds like a really great solution. Will this work with the official U-Boot or will it require a custom build that includes all those features you mentioned - pcie, nvme, usb, uefi?
I would imagine having this as the main bootloader on the NAND storage, which then automatically boots from available sources, first usb, if connected, then nvme, lastly failsafe from NAND itself. Thus not requiring an active serial console.
Of course the usage of nvme, usb, failsafe and order should be configurable.
And then the option for booting from SD or emmc still remains via the dip switches.
I guess, when done tinkering around, then better move to Emmc.
Fixed images, was missing CONFIG_PHY_MTK_XFI_TPHY=y
So now the BPI-R4 is fully part of script. A different linux is installed, based on dangowrt’s mt7988-for-next branch, so not rolling-stable yet. But the linux package now is up-gradable (when I build a newer version, or you build one yourself).
Only AccessPoint version until now.