it would be interesting to see how you upgraded the RAM chip at least - do please share - this is what openwrt is about 
...
I'll also share my 18.06 built images:
https://www.dropbox.com/s/u14j8en3xgehepa/openwrt-ramips-mt76x8-tplink_tl-wr841n-v14-squashfs-tftp-recovery.bin?dl=1 (initial tftp flash image)
https://www.dropbox.com/s/9a0wrysxampxddn/openwrt-dnscrypt-mt76x8-tplink_tl-wr841n-v14-squashfs-sysupgrade.bin?dl=1 (dnscrypt built in)
https://www.dropbox.com/s/7u1ty2y4a37vzlq/openwrt-DoH-mt76x8-tplink_tl-wr841n-v14-squashfs-sysupgrade.bin?dl=1 (https-dns-proxy built in)
I'm trying to backport this device into my 17.01 fork ( [Testing] lede-17.01 security backports for 4/32 devices ) but currently built images enter reboot loop so I'll need a serial console debug...)