I found a tip on the internet for removing the stickiness and gumminess that worked well for me. It is a cleaner/de-greaser called Purple Power. I bought my spray bottle at Walmart.
https://www.clean-rite.com/
I found it looking for something to use on a couple of old Tivoli Audio radios that had a rubber finish that turned gummy. Evidently a lot of old radios have this problem as there are a lot of discussions about this on the internet.
A couple of weeks ago I tried it on a spotting scope that had a rubberized coating and it worked great. All the gumminess was gone. It can leave a whitish residue on the surface, but further cleaning with the Purple Power took that off too.
I then used it on a digital SLR that had a rubberized coating that had become unbearably sticky. Worked great on that too.
For a couple of bucks, it might be worth a try.
I also have another product that I have used on my Landcruiser's steering wheel that had turned a bit gummy. It was more expensive though. It was called Rubber Buffer by a company called Hunter.
https://www.hunterboots.com/us/en_us/boot-care-accessories/rubber-boot-buffer/white/187
It was made for rubber boots, and I found out about it on a Toyota Landcruiser forum. It worked, but I don't think it worked any better than the Purple Power.
I will have to try David's homemade solution in the entry above next time. It seems there is no end of stuff that turns gummy and sticky in this Houston heat.
Harold
