I had a RX 6700XT when Portal with RTX first came out, and it was completely incapable of playing the game, even using upscaling and low settings.
Then late last year I upgraded to a RX 7900XT and tried the game again, and it played smoothly. I didn't take note at the time of the FPS, but the quality looked decent, I just wasn't that impressed with the lighting enhancements compared to the original game.
After seeing your post I launched the game again, and it took forever to load. Once I was able to get into the game, I noted the graphics looked very poor. There have been several Adrenalin versions since I last played, (currently on 24.4.1) but I also suspect there was a Steam update to the game, as I had to re-adjust all the graphics settings. You can access these by using Ctrl-X within the game. Some of them still don't work right. (probably need an nVidia card) but I did note that my Adrenalin metric overlay does not display FPS just as you reported.
Ryzen R7 5700X | B550 Gaming X | 2x16GB G.Skill 3600 | Radeon RX 7900XT
Ryzen R7 5700G | B550 Gaming X | 2x8GB G.Skill 4000 | Radeon Vega 8 IGP
Ryzen R5 5600 | B550 Gaming Edge | 4x8GB G.Skill 3600 | Radeon RX 6800XT