Some years back I traced the roots of this Sevastopol/Vastopol open tuning thing to:

"Sebastopol." Descriptive Fantaisie composed by Henry Worrall.
Published in separate versions for piano, banjo, and guitar
Boston, Oliver Ditson Co. 1888. Also published by C.H. Ditson in New York, J.E. Ditson in Philadelphia, Lyon and Healy in Chicago and John C. Haynes & Co. (also) in Boston.

No doubt it was also published in other places by other companies, for this was a very widespread and popular stage piece. It does indeed refer to the Crimean town and its role in the Crimean war, and uses harmonics, bugle effects, etc. to evoke stirring sounds of battle in performance.

(Interestingly the arrangement for banjo was done by banjo pioneer/craftsman S.S. Stewart.)

The sheet music gives the guitar tuning for "Sebastopol" as (low to high strings) D A D F# A D. The sheet music adds a direction for the guitarist to "Finger as if tuned in the ordinary manner."

The piece is without words. In tone it is a stage bravura piece, of the sort that used to be learned by advanced students for recitals. Because it was both formidable to play and relied on passages that weren't especially down-to-earth, the piece as written never passed into tradition.

But the open tuning caught fire and circulated among pickers almost at once, and there must have been enough performances by guitarists to get the name into circulation. Certainly by the 1920s "Sevastopol" (spelled thus by then) alternated with "Spanish" tuning (D G D G B D) as the most popular for both chord and slide guitarists who favored open tunings.

The placename Sebastopol meant little or nothing to most guitarists who, as years went on, had barely heard of Crimea or that war. Thus the word got bent into all kinds of shapes, Vestopol, Vastopol, Bestapol, etc., and the pronunciations would crack you up.

By the time I learned the tuning in the 1950s, nobody I knew called it anything but "Open D" --- just as the Spanish tuning (so called because it was used for Spanish Fandango) had become "Open G."

So far as I know there never was a standard traditional guitar piece called "Sevastopol" or any derivative. Libba Cotten's is one by that name, but over time I've heard people play various tunes called that. In short the name refers to the tuning, not the tune.

Bob