What case should a town be in after "civis"?

When “civis” is used to indicate an individual is from a town/city, what case should the town/city be in? I seem to be seeing examples in the nominative as well as other things. Egbert in Introduction to the Study of Latin Inscriptions (which, yes, is over a century old now) states that the name of the city will be in the ablative or, if singular of the 1st or 2nd declensions, then the genitive and seems to indicate that this applies to city names following civis, natione, genere, domo or natus in (p 97).The only example I saw following this, though, was “M. Liberius Victor cives Nervius” which certainly looks to me like “Nervius” is in the nominative. Perhaps Nervius is an adjective describing belonging to a people, rather than a noun indicating a place?

I’m including a number of examples from inscriptions below that are using “civis” in more or less the way I am looking at, but I can’t tell if the relevant descriptor is a place name noun, or an adjectival form (presumably derived from a region or a people).

As a secondary question, how does one go about deriving the adjectival form for a region, since that seems to be an appropriate way of doing this?

Does anyone know of examples where “civis” is definitely being used to identify belonging to a place using the noun form?

Examples from EDCS:

“D(is) M(anibus) s(acrum) / Q(uintus) Marcius / Suriacus / civis Teni/tanus / vix(it) an(nos) XLV”
Tenitanus appears to me to be in the nominative.

“D(is) M(anibus) / Q(uintus) Appius / Marcellus / c(ivis) Carthaginensis / ann(orum) XVI”
-is could be nominative or genitive, depending on the declension. I don’t know whether Carthaginensis is an adjective or a noun, though it sounds like it might have been a province in Hispania? If so it might be both a place noun and in the nominative following civis.

DD(is) M(anibus) / Terentius Marull(us?) / civ<i=E>s Brivines / vixit annis LXX
5th declension nominative is the only way I know to have -es be singular at all.

D(is) M(anibus) / P(ublius) Primit(i)us / Montanus / civ(is) Nem(etus) / vixit an(nos)
The editor of the inscription is assuming it should be in the nominative. Again, I don’t know the context well enough to know if this is a place or an adjectival descriptor of some kind.

Aurr(eli) M[a]rcianus Iiahin / civis Afer et Quintina / uxor eis vivi sibi / hanc p_scinam / virginem a se co<m=N>/paratam con/stituerunt

Iul(ius) Pi[3]/tinus civ/<i=E>s Dacus
This one solidly appears to be adjectival, indicating a person from Dacia.

D(is) M(anibus) / Titullinia / Pussitta / ci(vi)s Raeta / vix{s}it / annos XXXV / menses VIII / dies XV / TV
Raeta is the nominative form of the place, but given the nominative feminine of the person being referred to, I don’t think it would transform any in adjectival form in this case.

D(is) M(anibus) s(acrum) / L(ucius) Avianius / L(uci) f(ilius) Quir(ina) / Marcellus / cvis Hippo/niensis p(ius) v(ixit) a(nnos) / LXXXIII h(ic) s(itus) e(st)
Hipponiensis does appear to be adjectival for Hippo [Regius]._

Most seem to be adjectival.

Carthaginiensis is the adjectival form of Carthago, -inis, “Carthage”.

Tenitanus looks adjectival: -anus.

Brivines/ -etis might be adjectival. -es/-etis would be the declension type.

Raetia is the place name. Raetus looks adjectival.

Nervius is a ethnonym: https://en.wikipedia.org/wiki/Nervii

I wonder if civis simply means the individual had Roman citizenship, and doesn’t indicate citizenship in his/her local community. But “citizen of Rome” is civis Romanus. Note that in this expression, the adjectival form is used, which seems to be the usual form in the examples you cite.

-iensis and -anus are adjectival suffixes that could be added to place names. There are probably more.

What do you think the adjectival form would be for “Alauna”? I don’t really understand how to form an adjectival form of something.

Alaunensis would be my guess.