The Arduino MKR Zero: Arduino MKR ZERO (I2S bus & SD for sound, music & digital audio data) — Arduino Official Store.
That is a official Arduino board with good support. If you are a beginner, then this board is the most common and best supported board with more memory than the basic Arduino boards.
The RobotDyn SAMD21 M0-Mini seems to be Arduino M0 compatible. I think you have to use the normal Arduino IDE and set it as if it is a Arduino M0. I'm not sure how compatible the "M0" is with the other SAMD21 boards. The "M0" has its own bootloader.
Adafruit has a similar board: Adafruit Feather M0 Basic Proto - ATSAMD21 Cortex M0 : ID 2772 : $19.95 : Adafruit Industries, Unique & fun DIY electronics and kits. It uses its own development environment, so then you depend on Adafruit for bug fixes and support.
Sparkfun has a similar board: SparkFun SAMD21 Mini Breakout - DEV-13664 - SparkFun Electronics. They also have their own development environment.
There is also the Seeeduino XIAO: https://www.seeedstudio.com/Seeeduino-XIAO-Arduino-Microcontroller-SAMD21-Cortex-M0+-p-4426.html.
If you run into trouble with a non-Arduino board, and you ask us for help, then we do not know all the quirks of that board.
Arduino is working on a board with the RP2040. That might be a good choice in the future. The first versions might still have bugs, so it might take a year or two.
Can you tell what your project is ?