I also tested the ST506 emulator with an Acorn A410/I which has an onboard ST506 controller and it works perfectly as well.
Board and RISC-OS information
Revision board : D
MFM version : 4.33
OS Version : Debian 11.8 (bullseye)
RISC-OS version : 3.10
Machine : A410/I , 4 MByte of RAM, ARM3 CPU