From Step 2. Setting your Arduino IDE section at How to Add Seeed boards to Arduino IDE,
https://files.seeedstudio.com/arduino/package_seeeduino_boards_index.json
Both boards packages share the same package_seeeduino_boards_index.json name, resulting in a conflict for the Arduino IDE.
I suggest merging both packages into a single one with support for all the Seeed boards.
Thank you!
It seems other users are experiencing a similar issue.
See Confrict between "Seeed SAMD Boards" and "Seeeduino AVR".
It has been updated.
To add on to this. Seems like this happens at the STM32 level too. If you use one of the board packages you get the tools for the DFU and everything and the other one you don’t. I was able to compile originally but it didn’t know how to update and now I am having a conflict in the WString.h and itoa.h definition of utoa.
Just an FYI on this. I fixed this by basically rescrubbing my Arduino15 folder and redownloading the boards and then going and grabbing the Seeed SAMD pacakage and the Arduino M3 Cortex package. Just have to have the right ones or it vomits all over.