I used this one. Nothing fancy, but it already has USB plug so no need for extra encoders.
https://www.amazon.com/RetroArcade-us-ra-track-ball-2-inr2-Track-Ball-60/dp/B00OX0MKD8/ref=sr_1_1?keywords=2+inch+trackball&qid=1568406410&s=gateway&sr=8-1

It works good on the MAME games, just was hoping to use it for other systems.

Update: I managed to get several of the original trackball MAME games to work with the trackball. The problem was that my build has a few games that say they are MAME games, but are really just bad image copies, so the MAME protocols do not work. I deleted all of the bad copies and kept only the official MAME games.

So, I guess the next question is: Is it possible to make the trackball work for say an Atari 7800 version of Centipede, Millipede, Marble Madness, etc. ?

Yes, @Bernie-ran please share your set up. The trackball I bought has a built in usb encoder, but it does not work in MAME trackball games. Thanks.

By the way, I already did a search on this forum and found a whole lot of nothing to help. There is nothing about setting up a trackball with recalbox.

Hi, I am new to Recalbox and I installed a USB trackball in my cabinet control panel. The system is running on a Raspberry Pi 3 Model B. I can access Recalbox through my home computer over the network using the IP address, but I do not see a way to add the trackball setup. I see: Index, Monitoring, Audio, Bios, etc., but I do not see where to add a command for a trackball. It probably needs to be set up as a mouse, but I do not know how. Any help is appreciated and please be courteous to the newbie.

I am trying to add a photo of the steps I have taken, but the photo button on this page is not working.

Ok, so I know there are several treads about this topic. However, all of the recommendations are not working for me.
Background: I started with a Raspberry Pi 3 Model B. I installed [128gb]-Colbato.v2.DragonBlaze-Galisteo (took hours, but did it) and it uses the Recalbox OS. I set everything up and tested using my HDMI computer monitor (old 32" LCD TV). The controls work good, the content is amazing, and everything works great on my monitor. So, fast forward, I installed everything into the Arcade1Up cabinet and used and LCD to HDMI converter to use the current cabinet screen. I knew I was going to have to rotate the screen orientation (probably 270 degrees) so I looked up how to do it on this forum. There were many suggestions and the best ones were to look at the FAQs page for initial setup. I followed the steps in the FAQs page and it will not work for me.

What I need is the exact wording or script (step-by-step) to make this work. I hit F4 and then Alt F2 to get into the boot and typed everything exactly as it said and a few variations that I tried. Nothing is working. I am very new to this, so please be courteous.