There seems to be an overlap with the copula bi which can function as a copula in predicative noun phrases and in predicative locative phrases, possibly under the influence of English be.
However, de does not seem to function as an equative copula, and na does not seem to function as a locative copula.
Source: Ayafor 2008: 438
Source: Féral 1989: 77
Source: Féral 1989: 78
Source: Féral 1989: 78