German company Walimex supposedly making a slew of native M mounted lenses.

Walimex is one of the brand names of the Samyang/Rokinon/Bower/etc gang.

Most of the lenses listed as Canon M mount are actually their regular DSLR lenses fitted with a built-in adapter (ie. extension + bayonet M mount). So you don't gain anything in terms of size, compared to mounting the EF version on the EF/EF-M adapter.

Only a few of those lenses are truly designed for mirrorless, e.g. the 8mm fisheye, the 12mm f2, and others I may forget.
 
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