Sigma's Art EF35 is great...I just wish RF/future Arts can be lighter.
Sigma Art's for E-mount are way lighter then their old dslr versions...dunno about the 35, but I can certainly speak for the 85 f1.4 Art, as I compared my EF version + RF adapter to the Sony mount redesigned version; the EF version + RF adapter is 50% longer, and 100% heavier (double the weight!) compared to the E-mount version.
...but Canon wouldn't allow. And if they won't in the very short future, everyone should do their own considerations and choices.
OTH yes, the 35 Art is great, but as an owner of the 40 Art (yes, 40, not 50), let me just say that the 40 Art is as good as the RF 50 f1.2 L, while costing one third of it (and can cover both 35 and 50 focals, as it's almost as wide as the former, but it's distortion free like the latter so can be used on close portraits without significant effects on face perspective).
So from the glass standpoint, Sigma (but Tamron, too, on many lenses) has nothing less then the Canon glass, other then the price. Canon bodies are best on the market, period. But I value glass more then bodies, and I'm starting to be tired.