Hi @buzzardbait24! Thanks for getting back to me. I did some more research and it looks like the Kwikset SmartCode 888 Touchpad Electronic Deadbolt can be rekeyed to use the key you use on your other locks. I recommend reaching out to the manufacturer for whichever lock you are interested in and they can help explain this rekeying process that you're interested in!
Been researching similar questions myself. What I'm finding is that almost all modern/recent Kiwkset locks are able to be rekeyed yourself (I've done it once, super easy if you can follow instructions), it's a feature that is common in Kwikset locks (smart or otherwise).
However, the one I was looking at adding to my ring system most recently was a Yale model, which doesn't provide that feature. I call a local "lock & key" shop and asked them if I brought them an uninstalled smartlock from Yale, could they rekey it to match my current house key, and he said "sure, no problem". So while I haven't done it yet myself, it seems like it's likely something that can be done pretty easily at a shop like this or through a traditional locksmith. Hope that helps