I have currently rxTools with 11.2 on my emuNAND and 9.2 on sysNAND. I falsely already did "Section 1 - Prep work" from updating A9LH to B9S (because I did this with my 3ds which had A9LH [shoud've checked the 2DS too before]).
with the boot.3dsx of the upgrading guide, I get to the HB...