Signed up to post a warning about exactly this issue as of August 2019.
My wife and I just returned from the UK where we had a nightmare situation trying to rent a car with the Chase Sapphire Reserve. The rental company (Green Motion) refused to take the card as it was not embossed. Despite about 2 hours of phone calls with Chase and Green Motion corporate, we got nowhere and ended up having to rent the car with our Chase Freedom card. This cost us an extra £185 for the Green Motion collision insurance; we have no personal car insurance as we both have company cars, and so we rely on the Reserve included primary collision when we rent. Because we were stuck using our Freedom card, we had to purchase primary insurance to make sure we were covered.
Costly and miserable way to start our vacation. And despite explaining the situation in detail to Chase after returning, they offered us nothing other than a "we've never heard of that issue" excuse. Lousy treatment of long time customers (18 years), especially considering how expense the Reserve is on an annual basis.