Can a GPU be pushed into a PCIe slot?

It is unlikely to have an issue with the PCIe slot, but you can try connecting your GPU to another PCIe slot Red Dead Redemption PC Release

PCIe slots allow your motherboard to connect with your PC's most critical components and provide key functionality

pcie 40 gpu in 30 slot Equipped with the next-gen technology of WIFI 6E, PCIe , Realtek Ethernet, USB Gen 2x2 Type-C, PCIe Slot Q-Release, Four slots and

pcie 4 m2 in pcie 3 slot Elgato 4K Capture Utility Release Notes; Elgato 4K Capture This means that a device which requires PCIe will work in a PCIe or PCIe slot