Any board that writes and optionally reads serial data can be used for a pendant, but you need to consider the voltages of the two boards. If the voltage of the control board and the Arduino board are different, you may need to make provisions for 1) powering the Arduino board, and 2) changing the voltage of sending and/or receiving serial data. Typically, a 5V board can receive 3.3V data just fine, but if sending 5V data to a 3.3V board, I would, at minimum, add a voltage divider circuit (uses 2 resistors). Actually, given how cheap Arduino boards are, I’d simply pick a board that matches the voltage of the control board.
The other thing to consider is serial pins on the control board and what you need to do to enable them for your use. This will depend on your control board and somewhat on your usage scenario.
I use a Rambo 1.4 board and created a pendant. I run headless, so I was able to simply use the TX0/RX0 pins without any firmware modification. I use an Arduino nano which runs at 5V and matches the 5V of the Rambo board. If I was using the USB on the Rambo board, then I would have to enable a second serial port in the firmware. On the other hand, the last time I read about serial data and the SKR Pro 1.2 board, the V1 maintained firmware did not allow the enabling of enough serial ports to make a pendant work, BUT the latest Marlin release (used in the V1 daily builds), added additional serial port support. I don’t think this serial support has made it to the V1 release builds, but I’m not sure.