Is it somehow not possible to run OpenWRT openwrt-21.02.3-ath79-tiny-tplink_tl-mr3420-v2?
I've built a stripped image that fits, where I have stripped away wpad and other stuff in favour of usb2 and f2fs support. However, after flashing the image the device refuses to boot.
Luckily, recovering a bricked TL-MR3420v2 is not that complicated, and I managed to "unbrick" it by serving a factory image of OpenWRT v19.10 (ar71xx) - which then works.
Have I missed something, or is it suppose to not work?
My diffconfig is here: https://pastebin.com/CamGcTeh
Any help appreciated. 
Might be e.g. the kernel has gotten too large for the bootloader to handle. Best way to find out what's going on exactly would be to get serial up and check the boot log.
Yeah well, even though I do have serial cables that's a bigger engagement... We'll see.