Here is another debug log. Interesting that I got "id 5" when bricked, but "id 3" after mtk_uartboot:
Before running mtk_uartboot, this is my bricked log:
F0: 102B 0000
F6: 0000 0000
V0: 0000 0000 [0001]
00: 0000 0000
BP: 0400 0041 [0000]
G0: 1190 0000
T0: 0000 02D4 [000F]
Jump to BL
NOTICE: BL2: v2.9(release):OpenWrt v2023-07-24-00ac6db3-2 (mt7622-snand-1ddr)
NOTICE: BL2: Built : 21:45:35, Oct 9 2023
NOTICE: CPU: MT7622
NOTICE: WDT: Cold boot
NOTICE: WDT: disabled
NOTICE: SPI-NAND: FM35Q1GA (128MB)
ERROR: BL2: Failed to load image id 5 (-2)
Before bricking, I wasn't running snapshot. I'm happy to try other things to help debug!
Edit: realized the above was expected with bl2-for-debug-snand-issue.bin since I was using UBI but not yet moved to FIP in UBI.
I was able to load my 23.05.2 firmware with mtk_uartboot and openwrt-23.05.2-mediatek-mt7622-linksys_e8450-ubi-bl31-uboot.fip, force the performance governor in /etc/rc.local, reboot to u-boot, and then use the boot menu to write BL2 and FIP of the 23.05.2 release. After several software reboots, it seems stable so far.
Full command I used: ./mtk_uartboot-0.1.1/target/release/mtk_uartboot --brom-load-baudrate 115200 -s /dev/serial0 -p ./bl2-for-mtk_uartboot.bin --aarch64 -f ./openwrt-23.05.2-mediatek-mt7622-linksys_e8450-ubi-bl31-uboot.fip