Arghh! Disc lever shifter compatability

giblets

So looks like i have entered muppetry, been a few years out of riding (young kids), so getting back in and decided it would be good to upgrade the bike! So new rear discs, nice deal on M6100 on CRC, go to fit.... and guess what, they've totally changed the fitting.
My Left hand 3x M590 does not fit, reading up they have a new I-spec EV fitting.

So... is there any way I can get my M590 to fit with the m6100 lever (can I get a cover for the shifter window (who uses it anyway), or is it more serious than that?. I had a quick look at I-spec EV shifters and seem mostly 2 speed?
Or do I need to be looking at the 2nd disc market (I have a m615 on the other side)

The Rookie

According to this is can be made to fit.
https://bike.shimano.com/en-EU/product/component/deore-m6100/BL-M6100.html
Click the I-spec EV button to see how as here
https://bike.shimano.com/en-EU/technologies/component/details/new-tech-i-specev.html

Or just use your old lever with the new hose and calliper.

JBA

Just buy a 3-speed band on shifter. They aren’t indexed so any one will do.