i'm running on a WR841N v11 and dd-wrt v3.0-r44715 fw.
when I try to switch from dd-wrt to openwrt from Administration-> Firmware Upgrade, the device seems to flash, but on reboot I find the dd-wrt fw again.
the file I'm trying to flash is
openwrt-18.06.9-ar71xx-tiny-tl-wr841-v11-squashfs-factory.bin