Ah yes..the dreadaed "inverted bubble flare"...
I've had a few nightmares with those "inverted bubble flare" lines and fittings on the newer GM vehicles too!..they DO make adapters to allow "regular" SAE thread double flare lines screw into the wheel cylinders,etc..but GOOD LUCK finding any in stock at any parts store,no matter who's name is on the door!..if its sunday,better look for a rental car!..you will be driving it all over monday looking for those adapters...
It seems even the most experienced counterperson in the USA is not capable of choosing the right adapter out of the 30+ numbers out there!..We got frustrated at the shop I worked at--having to go to the store youself,and waste an hour trying different fittings--

--its not a part you can just describe over the phone and have delivered!..many times we'd cut the original line nar the wheel cylinder,and put a "normal" sae line nut on it,double flare it,and use a coupling to connect the two!--IF the original line was in decent enough shape to do so,that is..in many cases,they weren't..
Why GM and other manufacturers had to go "european" and use metcric fittings on all the lines on the cars and trucks--it was bad enough with SAE,NPT,Inverted flare, and other threads!?--like there wasn't enough confusion already?--and then "O" rings became all the rage

.

..there should be more standardization among critical parts like brake lines..but no,Volvo has their own,so does BMW,VW,and many other "weird" ones out there...
After working on my brakes,I am amazed any of us are alive--drum brakes use nothing more than flattenned "nails" and springs with washers that have cross shaped slots in them to hold the shoes on!--along with a few springs!--a little salt and rust,and FOINGG!--SKREEEEEEEECHHHH!!

--..and GM wheel cylinders with just a spring steel clip holding them on--now THAT was an engineering marvel,wasn't it??..

I bet they saved a nickel on bolts on every car--but they don't care if they rip out of the backing plates,and we can't stop in time..
I'd think something so critical as brakes would at LEAST use bolts a little fatter than those 1/8" nails!..and with all the myriad of different lines and flare fittings,it suprising to see how many "Jerry rigged" lines with compression unions,and other "Patch jobs" there are on the roads--and how rusted some are when you put the vehicle on a lift! makes you wonder how some of them stop at all!..
