When you say the talks got nowhere, how often was it brought up and what types of concerns did you raise/solutions did you propose? I completely understand and agree either way your point that sex isn’t worth significantly altering your relationships with kids and grandkids in a negative way. At the same time, humans have needs and desires that ideally will be fulfilled for an optimal life. If your wife won’t fulfill them (and worse won’t even discuss it or attempt to fulfill them) then you should at least be able to talk through it to hopefully come up with a solution to help everyone be happier.
If she has no desire to be intimate with you, would she be alright with you opening up the relationship? Just because she has turned off her desires, it’s unfair for her to expect you to do the same. That is likely not going to be an easy conversation, but she will at least know how serious you are about it and hopefully be glad you’re willing to still communicate. If fully open isn’t an option, then maybe a hall pass a few times per year. Still probably going to be a no from her, but worth a shot.
If neither of those are options, then perhaps maybe a sex doll and/or vr porn. Obviously not as good as the real thing, but vr porn is pretty crazy these days. I generally wouldn’t recommend porn because it tends to diminish the actual connection of a couple, but if that intimacy is already gone then the risk/reward ratio shifts greatly. It could be a way for you to release those urges and fulfill that desire without many of the negatives that go along either cheating. And you never know, maybe that would light a spark in her that could bring back some type of sexual relationship with the two of you.
If she is unwilling to discuss any of that or listen to your concerns, then unfortunately the issues go much deeper than just loss of sexual connection. If that’s the case then she has apparently lost interest in whether or not you are living a happy, fulfilling life. At that point marriage counseling seems like a good first step, if she’s even willing. Otherwise it sounds like she’s kind of given up on that aspect of her life and just wants the benefits that go along with being married with none of the sacrifices, and that’s not how it supposed to work. In that case, good luck with however you decide to proceed. I hope everything works out for you.