nevellii

Nobody has been able to grow C. nevelli and there's a bit of a history with this plant, here's the summary:

1) It used to be a popular aquarium plant.
2) But that turned out to be the instead the naturally occurring hybrid we refer to C.x williamsii.
3) Nobody has ever been able to grow the real nevelli long term.
4) We found out later it dries up for several months a year this the pant has to have a rest period.
5) The leaf litter trick was found after that was written

So, we do't have any real cultivation information that allows is to keep these long term. There has been no update to this since 2010

Also, it isn't known from that many places in Sri Lanka, perhaps there's chance that it's different from what we have had so far as NEV.

"Cryptocoryne nevillii is well known name for a popular aquarium plant, but already in 1928, Petch put severe doubt on the identity of the plants known by this name. The problem was not cleared until 1976, when plants from the original locality, found by Dan Nicolson, were discussed by Niels Jacobsen. Until now, many aquarists and also dealers and nurseries still use this name for the plant which must give up its name and is now called Cryptocoryne �willisii. The 'real nevillii' is not suited for the aquarium. Besides Nicolson's collection, other localities are found by Kundu & Balakrishnan, Davidse & Sumithraarachci and Faden & Faden. From the latter, plants are also in cultivation."

https://crypts.home.xs4all.nl/Cryptocoryne/Gallery/nev/nev.html