I had a go with dz80, and a later version z80dasm but neither handled Z180 opcodes. I think I would have to recompile z80dasm to get a version which did.

I was recommended ghidra, which I had heard of from Jaques who added Z8000 to the machines it supports.

I found Ghidra non-trivial to pick up, but that's because it is a much more powerful program. I will use it for  analysing other binaries in future.

The board has a PC-compatible floppy disc controller, but also an I2C EEPROM so there will be I2C code in there as well.