ANT+ is not natively supported on Rog Phone 2. But if someone is active in sports, ANT+ is an important addition to use with sport watches, cycling computers, interactive trainers. Heart rate monitors with advanced sport metrics use ANT+.
There is a neat and not a bulky solution. Garmin ANT+ usb stick combined with USB A to USB C adapter (I use the one from Samsung) works immediately. All that is needed is to download ANT+ radio service, plugins service and USB service apps from Play Store. Stick works on both USB ports on the phone. I use the side port so my phone can stand in portrait mode.
In my case there are 3 devices connected simultaneously. Heart rate monitor, cadence sensor and interactive cycling trainer. Everything works perfect.