At least for me using the SPL loader does not work either.
~/b/rkdeveloptool (master)> sudo ./rkdeveloptool ld
DevNo=1 Vid=0x2207,Pid=0x350b,LocationID=101 Maskrom
~/b/rkdeveloptool (master)> sudo ./rkdeveloptool db ~/Downloads/rk3588_spl_loader_v1.08.111.bin
Creating Comm Object failed!
~/b/rkdeveloptool (master) [1]>
I also had to manually apply https://github.com/rockchip-linux/rkdeveloptool/pull/67/commits/26aaf9d283cacf589aafe71fcce0a204635c526b to make the tool compile.