I did it!
I want to thank all the members that helped me on this, your help has been precious, really.
Finally I was able to build "my" oscam, with pcsc and it's working fine with my Onlikey external reader with my second card!
I admit that I feel a bit stupid for at least one issue I had, the "Segmentation fault" error using my built "non .debug" oscam!
Guess what? The issue was the #@&% Filezilla client I was using on Linux that, evidently, did not transfer the bin program in binary mode!!! (linux to linux!)
To my defense, I've been using filezilla for YEARS, many years, on windows and never, ever had this kind of issue. Also, the fact that, for whatever reason, the .debug version of the bin file was transferred properly added more confusion.
For the record, the very same (non .debug) executable is transferred properly using filezilla from a windows machine to the Vu+ box.
The protocol mismatch problem was due to some mess up (likely by me, but I'm not 100% sure of origin of it) in the libpcsclite1 library, as correctly pointed out by blzr, that I want to thank for the oscam with pcsc he provided in the above post. I've not tested it, I already installed "my" built one and after days struggling...I'm keeping it , hopefully it will help other users that need a second/external card reader in VU+ ARM boxes.
OK, it has been a long "battle", nevertheless I enjoyed it (maybe I'm masochist?! )....well, at least at the end!
The ability to build oscam is nice, I doubt I will ever need again in the near future, but it's nice to have some little independence in messing up with my sat box.
Once again, thank you all.
SatRider