I pulled the MT7668 drivers from the FireTV 4k Stick, 2nd gen Cube and Echo Studio.
The FireTV 4k Stick uses Kernel 4.4, and it includes an almost identical version of the CE v0.0.1.00_2021011401 driver. The Echo Studio also used kernel 4.4, with identical drivers to the 4k Stick.
The 2nd gen Cube used Android kernel 4.9. Although the 1st firmware from 2019 has the same driver version as the 4k Stick / Echo Studio, all the Mt7668 drivers after that are significantly different even though they share the same driver version numbers.
Would it be possible to either test the oldest driver for the Cube
2nd gen Cube MT7668 v0.0.1.00_2019111401
/mt7668/FireTVCube/FireTVCubeGen2-7.2.3.4-20210322/mt76x8/
or the newest version for the Cube
2nd gen Cube MT7668 v0.0.1.00_2022121401
/mt7668/FireTVCube/FireTVCubeGen2-7.6.4.6-20230601/mt76x8/
One of the Echo Studios firmware also included a very old and much more basic version of the driver v0.0.0.24_2017052601. Maybe the oldest version has a better chance of compatibility?
/mt7668/EchoStudio/Echo_Studio_src-6.5.3.7-20200324/
I’ve included all the source here