Here is the full list of all 15 Portal with RTX achievements. It takes around 6-8 hours to unlock all of the achievements on Windows.
Acquire the fully powered Aperture Science Handheld Portal Device.
Detach security cameras from the walls.
Jump 300 feet.
..?
Knock down a turret with another turret.
Fall 30,000 feet.
Earn gold medals on all Portal challenges.
Earn bronze medals on all Portal challenges.
Earn silver medals on all Portal challenges.
Beat all six Portal advanced maps.
Beat four Portal advanced maps.
Beat two Portal advanced maps.
Complete Portal.
Make the correct party escort submission position decision.
Do whatever it takes to survive.