Each build of the Android OS is a bit different so you will need to pay attention to the one you are using.
When you adb shell into a device you cannot just look around like you used to, in other words many commands don’t work like “ls”. If you have rooted the device and have su installed you can type “su” to get access to many more commands that will help you work on the device. But you need to pay attention, sometimes typing “su” gets you a new prompt like root@whatever sometimes you get a “#” instead of “$” as your only indicator.
Just saying you have to get used to the differences for each version and build of the OS.
If you run into issues with jadx-gui not showing code use the following
jadx-gui –show-bad-code xxxx.apk