I think you’re better off just changing to a different board if that’s what you want. There’s even an eagle schematic/board kit floating around for an arduino shield that makes a reasonable start if you’d like to make your own from scratch (which might be a fun project…using an S3 to do isolation routing on a new board for an S3…)
There are a number of sources of GRBL boards, some much better than others. I wasted a lot of time with a couple of particularly bad ones which turned out to be poor copies of better boards, but got me annoyed enough to just go all the way to a board that did exactly what I wanted instead of halfway there.
Junk: (terrible support, and awful connectors) https://www.ebay.com/itm/KEYESTUDIO-CNC-GRBL-0-9-Microcontroller-Board-for-Arduino-Laser-Engraving-Shield/253941089007?hash=item3b201182ef:g:GSUAAOSwVYhb49Xu
Junk: (Just…no. All the boards that have this look come from the same board design, which is outdated for current GRBL, and I haven’t seen one yet that wasn’t really poorly made) https://www.ebay.com/itm/CNC-Shield-V3-0-4Pcs-A4988-Motor-Driver-Kit-for-Arduino-UNO-GRBL-Engraver-MCU/264330280631?hash=item3d8b4ffeb7:g:zggAAOSwww5c2sDI
My favorite is actually this one → https://shop.tomsrobotics.com/product/grbl32-3-axis-cnc-controller-g32f13-150khz/
It uses a (very well done) 32bit port of GRBL on ARM. Onboard or offboard drivers, every useful pin is broken out, and there are some additional GPIO’s available (and can be used via g-code additions). It has a few small nuances to be aware of around enabling the spindle pwm, but overall it’s a really well done board. It’s a little bit of a hassle to set up inductive limit switches, but that’s true of basically every board I’ve seen (inputs are 5v, and most inductive switches are 6-30v input/output…5v input switches appear to actually be “binned” 6v switches, and I’ve had two such switches stop working at 5v after a while) One of the things I like about this board is that it uses a standard STM32 Blue Pill as a CPU board, which plugs right in. That gives you some additional flexibility, as there are variants of that with significantly more memory if you’re feeling like adding some features.
My second favorite is this one: https://supergerbil.com/product/starter-super-gerbil-cnc-controller/
This one is also GRBL on ARM, but the port they are using is not particularly clean. I had to make changes to their firmware (that I believe they now include in their code) to make it work properly with lightburn, CM, and a couple other senders. It does have some support in the hardware for a toolchanger, but the software isn’t complete for that. It’s possible to put the GRBL32 port from the Tom’s board onto this one, but requires remapping the IO which takes a little code work to do (and a really irritating development environment). My understanding is there is a new version of this board coming, but I don’t know when. The board is fully opto-isolated, which is a nice addition, and is also polarity independent on most inputs. Not the easiest board to set up, as it requires a number of input power supplies, but very flexible, as it supports multiple power supplies and voltages for different things on the board. Has a nice spindle controller option that may allow you to forgo a VFD in comes cases. It will do onboard drivers, or offboard. This board that the same issues every other board does with non-5v inductive switches. I used this board for quite a while until an unfortunate accident had me looking elsewhere.
There’s a really nice view of the board and it’s options here:
https://supergerbil.com/2019/05/sg-board-configuration/
Here’s the thread where I replaced my Keye’s board with supergerbil.
Here’s where I made the original jump from the CM board to the keyes studio board.