Excellent guide! I have been looking for something like this a couple of days ago, eventually I managed to do the same steps you described (from various sources, same as you). Have been planning also to make a similar post as yours, but unfortunately I haven't managed to succeed with the flashing, I softbricked twice my S10...I just installed LOS with TWRP and Magisk on my S10 and everything seems to be working fine.
Everything seems right on, until I flash the custom OS (indeed I tried Pixel Experience Plus, but from my understanding it should've mattered, even the patched boot.img from lineageOS is referenced on the PE thread).
Could you please tell me, what was the version of the stock firmware that you have used? which security update? I tried with DTI8... (second time I also tried, but couldn't flash the previous version of the stock firmware through Odin, it kept returning an error mentioning "kernel, binary" something (sorry, noob, not familiar with the terms, can't remember exactly)
Thanks!