Can't boot from a microSD card

[PineFLOWn]

I can't figure out how to boot from a microSD card. Looking online, most of the relevant information I can find says that the PinePhone Pro's default settings are to boot from the microSD card, and only boot from the eMMC is not microSD card is present.



I've copied a postmarketOS image on the microSD card, putting it on the phone (yes, I checked it's the right slot!), and then turned it on. It just boots to the factory KDE OS.



I've been told to hold the up button when the phone vibrates during boot, but the phone does not vibrate at any point when starting up. The top LED flashes white very briefly, moments later a mouse pointer appears briefly, then the speakers make a light "thud", and finally I see the lock screen of the OS on the MMC.



I tried holding the up key (and also with down key), but the results never vary. I grabbed the `-installer` image from here: https://images.postmarketos.org/bpo/v21....0406-1001/



Here's what the partitions looks like on the mSD:

Code:

$ lsblk | grep -v nvme

NAME        MAJ:MIN RM  SIZE RO TYPE  MOUNTPOINTS

mmcblk0    179:0    0 119.1G  0 disk

├─mmcblk0p1 179:1    0  243M  0 part

├─mmcblk0p2 179:2    0    2G  0 part

└─mmcblk0p3 179:3    0  2.5G  0 part

│ └─root    254:0    0 921.6G  0 crypt /

  └─swap    254:1    0    32G  0 crypt [SWAP]

I tried copying the image over it from scratch a few times, always same results.



Any ideas?

I recently had to reinstall TowBoot for some reason in order to get it to boot to the mSD properly when holding Volume Down at startup.
It seems that after a while the first install of TowBoot stopped working correctly.