Realtek RTS522A pci-e SD-Card reader

I'm trying to get the above-mentioned card reader up and running in my NUC8 (but according to the internet it's also used in other devices (e.g. Lenovo L430...)).
This reader is supported in Linux distributions (e.g. Mint 19) and probably also in OpenWRT if it is selected in make kernel_menuconfig and built into the kernel. But it doesn't have selectable module in make menuconfig.

If I compile the whole system using Buildingsystem (chosen version 22.03.2) with the selected reader in kernel_menuconfig (as "<*>"), I see that the memory card inserted into the slot is detected and is assigned the device path /dev/mmcblk0p1, but for some reason the OS cannot detect/start init and restarts.
If I compile the given reader as a kernel module ("<M>" in kernel_menuconfig) and use it in an already functional OpenWRT (from Image Selector, v22.03.2), the system will restart immediately after i try modprobe rtsx-pci.

I also tried to create a package similarly like someone did in this topic (copy source code files from ./openwrt/build_dir/target-x86_64_musl/linux-x86_64/linux-5.10.146/drivers/misc (there is his source code) to ./package/kernel/rts522x/src and create new Makefile with content similar to that in that topic (renamed package name + filename in FILES list, but make package/kernel/rts522x/compile throws: "make[2]: Nothing to be done for 'compile'."

Is there any way to get the reader up running, ideally as a loadable kernel module?