That’s a question you really need to ask your local Porsche dealer(s). Talk to the service manager, tell them you’re looking at used 911’s, and ask what extended warranty plans they can offer, if any.
Then, compare the costs to how much more you might pay for a CPO car, and weigh your options. All part of the buying process.
Also, for these types of 911 specific questions you’d be well advised to spend some time over on the Porsche forums (Rennlist, etc.), where you’ll find many more details on all things Porsche. Search and/or ask there about 991.2 extended warranty options and I’m sure you’ll get a range of ideas and opinions.