How to change language of latest firmware of AC68U?

[Kinomoto-san]

I signed on after I found a way to set the language to English.
Thanks to the thread I learned about the ssh login and the nvram utility.
I tried, but could not change preferred_lang from JP, as others reported already. I'm using the latest firmware (3.0.0.4.384_32799, as of Dec. 9 2018).
Once it actually did show =EN, but only once, it didn't change anything, and it didn't survive a reboot. I've also found a 'temp_lang' setting, which *will* stay at =EN if set so, but it doesn't seem to do anything interesting.
HOWEVER: I tried this: "nvram set preferred_lang=", i.e. I set it to empty. 'nvram show' showed that it stayed that way, also after nvram commit.
I then refreshed the web page (I was also logged in via the gui), and lo and behold, it changed to English!
I have not rebooted. I don't know if it survives a reboot, but this thing never need reboots anyway - this is my second AC68U, I've had another one running for years non-stop in Japan (and that one had the normal language selection tab, so I never imagined that the new second one wouldn't too). Anyway, my problem is solved - I can struggle through the Japanese UI, but it's is definitely easier with the English version.

TL;DR;
This fixed it for me:
ssh in as admin
nvram set preferred_lang=
nvram show|grep lang
verify that it's still empty
nvram commit
nvram show|grep lang
verify that it's still empty
Don't reboot (don't know if this makes it reverse again - I haven't tried)
Refresh web browser UI, or log in fresh.
It should change to English.

Hello @Tor, I tried your workaround and it worked like a charm with my RT-AC85U !!
And it survived a reboot !
There is no dropdown menu but the GUI is in english now (was in Japanese).
Thanks a lot !!!