TrainerDX says that card was first observed in a submitted Zwift log file in game version 1.39 (May 2023) and it is on the Basic profile. They would need to add it to a list and ship a game update to change the profile.
You can change the resolution by manually editing the game preferences but you can’t change the profile. You can tweak a few things in the config to increase the graphics quality but you can’t put it on Ultra profile yourself.
I imagine this was an oversight so it’s possible we can get their attention on it sooner rather than later.
If you want to check the profile of any card you can find it on the GPU Profiles tab on trainerdx.com. That relies on someone submitting a log file that reveals the profile, but it should be accurate for any popular product.
In the world of the older Intel powered Apple Mac Pro workstations it was somewhat common for folks to flash the RX6950XT with the bios of a reference RX6900XT and that would allow them to work under MacOS (which never supported the 6950, only the 6900XT and W6900 32GB).
If you were really desperate you could look into that - but I do not recommend it unless you are very savvy and have another computer you can use to do it. This might get Zwift to recognise it as well by fooling it into thinking the card is a 6900. You should check with the folk on Macrumors how their cards work under windows also before you try that.