The last scarpa SLs owned lasted less than a year. The sole tread wore down badly and the instep snapped right across. No crack to full width crack in one step! Quality dropped badly back then.
I've steered away from scarpa for years until last summer I got a pair of trail shoes. A plasticky bit on the side of the sole unit started peeling very quickly and a hole in the inside of the body of the shoe top.
Imho scarpa are iffy at times.
There's many glues you can use for peeled rubber. My advice is preventive gluing. Act at the earliest sign of peeling. Once it's peeled away more than a cm or so the rubber can stretch and it might not glue down flat. You can buy special shoe glue but tbh a good superglue suitable for rubber might be just as good. I use a gorilla glue that's described as flexible. I figure it'll stretch with the flex of the shoe.
I've just used it to seal slit holes at the crease lines in the instep region of the trail shoe body. Fabric with goretex lining. Gluing the long, thin holes with flexible glue will protect the membrane I think. Solomon shoes that have lasted surprisingly long for me.
Leather is about keeping it from drying out. "Moisturising " it with a wax or cream that gets into the fibres are good. Nikwax is good but others work too. I once heard dubbin rots the threads. I had a few boots fail at the threads but not sure that's why. Usual advice about drying out slowly away from strong heat like fires and radiators. That can crack the leather but also over dries it ime. Dry with the innersole out of the boot. Newspaper in the boot helps.
I know all the theories of maintaining leather boots but I never did it very often and tbh it didn't harm the boot as much as poor quality of major brands that shipped production away from Italy to Asia or elsewhere without getting quality matters right. As a result the boots failed at the soles through use, but not a lot of use. First SLs lasted nearly 10 years, second 18 months, third less than 12 months. No fourth one.