What OS are you using?
And what version of the os?
And are you trying to convert from the SD card directly, or are you moving the files to your computer first? ( strongly recommend the latter.)
In iOS you can import .CR3 files straight off the SD card in to Photos.
I believe CR3 support was added in macOS 10.14.1
I don’t know what you mean by ‘dng file converter’ - the CR3 format is not dng. CR3 is supported in Adobe Camera Raw, which is a free download.
Canon has its own Digital Photo Professional (DPP) converter app, which has supported the M50 on macOS for over a year.
Here’s the tutorial page: