(info. : take care ! if you have buy Bannerlord, you have maybe with Mount&Blade as free gift.... but isn't Mount&Blade:Warband "standalone"...is M&Blade first edition !
so : all Warband mods doesn't work with !!!)

hi guys !
all gamers say "use the Steam workshop"... but if that can't work,
my TIPS (used by rookies of Warband for play on old mods) :

TIP 1/ don't use workshop ! (Workshop : it's better for Updated mods, like multiplayers mod)
download the Gekokujo mod 3.1 (on NEXUS or MODDB websites):
MODDB link (already patched !) https://www.moddb.com/mods/gekokujo/downloads/gekokujo-31-with-suguroku-and-3-shogun-armor
NEXUS link (need patch manually) https://www.nexusmods.com/mbwarband/mods/3816?tab=files
don't use "workshop" and put the MOD in that Warband-steam file "...\Steam\steamapps\common\MountBlade Warband\Modules\gekokujo"
and after no problem : you found your mod in the Steam-Warband launcher !

TIP 2/ if you have Downloaded with Workshop (but you don't know where the mod is installed) your Gekokujo is here :
Steam\steamapps\workshop\content\48700\285786182
AND
if you have a problem for launch WARBAND in "OFFLINE STEAM MODE"
here a solution :
https://steamhost.cn/steamcommunity_com/app/48700/discussions/3/1846946102866174420/
don't do all the manipulation, but just copy-paste OR install your mods in :
"...\Steam\steamapps\common\MountBlade Warband\Modules"
and Unsubscribing from Steam Workshop Modifications.
(FOR INFO : if you use "family shared" of Steam, for play at Warband,
because a friend give you the access for the game... YOU NEED TO BE ONLINE !
only the player who have buy Warband, can play in "OFFLINE" mode !
But : you can, disconnect web connection after launch a solo game )

TIP 3/ your saves Warband file (for recover your saves) the save games are located in
"DISK letters:\Users\...\My Documents\Mount&Blade Warband Savegames\gekokujo"
(you can copy that somewhere... and when you have a problem you can recover your save game !) if you have steam warband + an old version non-steam Warband :
the saved game file it's the same ! so take care about that ;)

TIP 4/ if your mod doesn't work with steam workshop OR steam warband module...ONLY !
(it's the solution if you want to play at the "Daimyo edition" Gekokujo...but it's not the official mod, it's a modification !)
use an old version of Warband outside of Steam :
-1 - take the 1.158 Warband install on Talewords website (or other version of Warband, depend of your mod !)
(Gekokujo 3.1 is made for the 1.158 version of Warband-AND for Daimyo, i don't know !)

- 2 - after, go on steam, right click on Warband (like for your proprieties)
and search "CD KEY" - you have a button for "copy-paste" the key.

- 3 - launch Warband and enter you Key when the game demand.
(if the key isnt in the good format - i give some links at end of message for convert the key)

- 4 - after go download the Gekokujo mod 3.1 (on Nexus or Moddb : search Gekokujo 3.1) and put that in : warband/module folder of your "new-old" warband !

I HAVE TEST TIP N°4 technique in first (because before : don't work for me !)
I HAVE TEST TIP N°1 technique today (me : ive copy-paste my 3.1 GEK. mod
from my C:install TO my Steam/warband/modules that work well too !)

good luck boys !
and now : go as a ronin, samurai or daimyo across the Japan...
and maybe a day, in a new "Gekokujo" on Bannerlord ;)

- Links for convert (only if your Steam-warband-key dont work) :
go to :
https://www.taleworlds.com/en/Account/Login
select "my account" and "login with steam" then go on this link :
http://www.taleworlds.com/en/Account/ConvertSerial

more infos (about serial key convert) if needed :
https://forums.taleworlds.com/index.php?threads/steam-warband-and-5x5-cd-keys-guide.152065/
https://forums.taleworlds.com/index.php?threads/no-serial-key-for-multiplayer-help.239350/
https://forums.taleworlds.com/index.php?threads/no-serial-key-for-multiplayer-help.239350/