Okay, I solved my Tankstick issues, mostly, in case anyone else is having difficulty.
First thing, however – the trackball does NOT work in MAME4ALL, period. I understand some folks have gotten it to work by unplugging the other USB connector first, and then starting MAME4ALL. Remember, the Tankstick uses two USB ports – one for the joysticks, one for the trackball. I haven’t tried this as it’s too much of a pain in my rear and is a work-around at best. Now having said that, the trackball works fine in AdvMAME, so I play all my trackball games using that emulator instead.
How I got the joysticks working properly was to go into the Retropie Setup menu and DISABLE the Xarcade2jstick service. This is weird because I’ve been using that option ENABLED since 3.0 Beta 1 without problems. However, with it enabled, I cannot get any Retroarch emulators to recognize the Tankstick buttons or joystick. Again, this was NOT a problem until I updated to the latest binaries a few days ago.
Anyway, with the Xarcade2jstick service disabled, I then used the Retropie Setup menu to install the joypad configurations (not sure if this is actually needed or not) and then everything works okay. In MAME4ALL and AdvMAME I had to reconfigure the inputs the first time I launched them, and then customize anything per game the first time I played them, but at least it all works again.
Again, it’s kind of a pain and I did not have to do this with prior versions of the 3.0 beta – the Xarcade2jstick service basically took care of it all. But it’s all working now after going through the motions to configure things manually.