I got a Canon 35mm F/2.8 Macro IS STM for a T-6, which is on backorder, but they said they will let me know when it ships.
I'm not a Canon shooter, but I've read here on UHH that this may be among the EF lenses that Canon has recently discontinued. So I suspect there is limited availability and you might want to buy it it from someone who still has it in stock! Canon lists it as "unavailable." I'd not expect a particularly happy ending with a backorder for an out of production item, even from Adorama or B&H.