According to a report from Android Police, it seems that the unlocked HTC 10 handsets are now starting to receiving the Android 8.0 Oreo update via OTA and RUU. For those who can’t wait for the OTA to be pushed to their phones, there is the RUU version available via HTC’s website (clicking this link will start the download), so that could be worth checking out.
As Android Police notes, downloading the update will wipe your phone so you want to make sure that all your data has been backed up, whether it be on your computer, on a flash drive, or in the cloud before proceeding, lest something goes wrong and you lose everything in the process.
It is unclear as to when the update will find its way to the carrier variants of the HTC 10, but it will most likely be later as carriers usually need to vet the update themselves first before signing off on releasing it.