You probably have a 'Processor with graphics' model CPU.
At a guess, your monitor is connected to it on the motherboard port & so not using the 7900xt would be a reason for the low fps?
Ryzen 5 5600x, B550 aorus pro ac, Hyper 212 black, 2 x 16gb F4-3600c16dgtzn kit, NM790 2TB, Nitro+RX6900XT, RM850, Win.10 Pro., LC27G55T..