The Cyrillic letter Ge (Г) is often Anglicised as ⟨g⟩. However, this depends on its pronunciation within each source language. Ge in Ukrainian is closest to the English /h/, and is therefore translated as ⟨h⟩. Keep in mind that an Anglicisation system is intended for English speakers.
Ge in Belarusian is often Anglicised as ⟨h⟩ (as in the name Siarhei), despite being closer to the English ⟨g⟩. Why is this?