LG K20 receiving the Android 8.1 Oreo update at AT&T
The bad news is the update contains a much older August security patch and we're not sure that AT&T and LG will continue to offer newer security patches to the K20. Other changes mentioned by AT&T include FirstNet IOC2 and Mobile Hotspot APN, but that's about it.
It's also worth noting that this is a pretty sizable download (1.45GB), so make sure you have enough free storage before attempting to update your phone. If you're considering keeping your LG K20 for one more year, you should know that Android 8.1 Oreo is likely to be the last major OS update this smartphone will receive.