It can be done if you have the right nav system, but not recommended as there is a high chance of bricking your system.
Whilst I successfully installed the upgrade in my old NX, there were a number of people that had failures.
You would be better off contacted your nearest Lexus centre and enquiring about the CarPlay upgrade cost. From what others have said it is anything from ‘free’ if you are having a service up to around £100 (as it does take quite a while to do). This info may be out of date though.
l’ve just looked on the tech website and the software looks like it is still there to download - I don’t have a current subscription to check though. From memory you download the instructions and the download links are contained within these instructions.