Hi, many thanks for the eLeMeNt ZX/MB version!
Unfortunately the LnxSpec emulator does not fully reflect some non-ZXi ports. As written above, on the eLeMeNt hardware the port 255 is ZX-based when read (IN), so there is an extra "shadow" port for Timex, timex 0xFF port is writeable only and readable is at port 0x9FFD.
The current beta should be changed, instead of IN A,(255) use LD BC,0x9FFD and IN A,(C).
Another method, without previous reading IN A,..., is simply to write to the 0xFF port a timex graphics mode, value "2".
Please check the page 19 of the ProgRef manual
https://docs.google.com/document/d/1NJB_z3zVorTfmEj2JAS3QtAx_zbpkdCAAptHSnOOzkU/...
And the third solution: the ZXi configuration port will be improved, a setup bit will be added to make the port 255 fully timex readable, but it will take some little time...