The Badger v2.6.0 by Jason Buechler

REQUIREMENTS:

A relatively recently updated Windows 10 computer
Administrator privileges for the user running the script
All network adapters, besides one ethernet, to be disabled/disconnected
Several files that I'm not hosting or including because I have no idea what the licenses are and am not interested in taking that obligation on... BUT, they're easy to find. Grab them from this famous instructional page: https://www.bayareatechpros.com/ac1900-to-ac68u/
Optional (but recommended) is an rt-ac68u CFE .bin file of the version you desire. The most commonly needed one can be found in the "tmo2ac68u" package here: https://wiki.dd-wrt.com/wiki/index.php/Asus_T-Mobile_Cellspot or via a little googling.

MAKE IT DO:

verify you've collected all the files in one place (see below)
right click badger.ps1 and "Run with PowerShell"
if it opens in PowerShell ISE, you'll see the green-text note at the top saying to run it using the green play/triangle button
however you run it, if it determines you need to do so, it will alert you that it will relaunch itself properly

NECESSARY FILES:

The Badger's scripts -----> https://github.com/jasonbuechler/asus-rebadger/releases
- badger.ps1
- bits/*.ps1
downloads from bayareatechpros
- FW_RT_AC68U_30043763626.trx ........... (MD5: C9D544EFD51DAD31C7A0E533DBD2005B)
- mtd-write ............................. (MD5: DC162789E82618AC4E0F6A252A083F8F)
- TM-AC1900_3.0.0.4_376_1703-g0ffdbba.trx (MD5: E617E8E4326D61EF7DECC751FA3D40D4)
optional download from dd-wrt (or competant googling)
- rt-ac68u_1.0.2.0_us.bin or similarly named CFE file of version 1.0.2.0
- (if you don't download this file in advance, you'll be prompted to visit cfeditor.pipeline.sh in the middle of the process)

Demo

...And basically everything else too.