Interesting. I'm on Mac OS13 and I did not get the notificaitons. I rechecked the help/updates and it is still greyed out. I'll keep watching to see if it becomes available. In the mean time I downloaded the trial vs of PSE2020 and it came with ARC 11.3 which supports Canon RP_CR3.
I then purchased it as it was on black Friday sale for only $59.99 USD. Well worth it for the convience of not having to use DNG Convert. Plus it looks like PSE2020 has some interesting new features. 🙂
You can see in my link that the Canon RP is supported, even with the 11.3 version.
I am waiting to see what the version 11.4 offers beside new camera support.
Edit:
I have now the 11.4 ACR in PSE2019 and the 11.3 one in PSE2020... I have already had two updates for PSE2020, so that may come soon. I am disappointed that the two new sliders in the basic tab of the full PS ACR are not there.