You will have to remove this dkms package because it's not compatible with the kernel in Pop!_OS. We update the kernel regularly, so there's no need to install a backported driver. The realtek drivers are built into the kernel.
I purchased an Intel AX210 (M.2 card for around €25) to replace the realtek card so that I can get stable Bluetooth and WiFi connection. I tried the drivers for rtl8821 but they still weren't good.