No, the OM System OM-5 is not compatible with the ProGrade Digital CFexpress Type B Gold 128GB.
OM System OM-5 has an SD-only card slot (no CFexpress support of any type). Its own spec page confirms only SD/SDHC/SDXC card compatibility — CFexpress Type B uses a physically different connector and cannot be inserted into an SD slot.
What works instead
See all compatible camera for the OM System OM-5 →“SD Memory Card (SDHC, SDXC, UHS-I, UHS-II compatible)”
Last verified:
Compatibility inferred from spec rule (citations above are manufacturer-verified)