I have potty trained using the outdoors ONLY but it took basically being home & constantly aware
for two weeks. As soon as she woke up from napping, I'd take her out and effusively praise her as soon as she urinated or defecated outdoors then, back inside. I would take her out regardless of any signals every couple of hours and I did not feed late in the evening--making sure to get her out as late as possible, though. A few accidents on the first day or two, but she learned quickly and by week 2 was coming over to me to stare at me or whimper and I knew. I haven't had a dog who did not thrive on cold and snow in a long time, so I never felt compelled to teach them to use any garage or other alternative. I did kennel her early on a bit if I thought I was going to be gone a bit too long (week 3) with urine pads, but she soon was able to hold her urine overnight and through the day if I was careful about long walks before leaving. Young puppies can't hold their urine more than a few hours, but that capacity does "grow" with them (fortunately).
Good luck.