Palantir Technologies Inc. is expected to fetch a lofty valuation in its transition to a public company despite an unusually aggressive governance structure, in the latest sign of investors’ voracious appetite for new shares.

The data-mining-software specialist is eschewing the traditional IPO route and going public through a direct listing, in which a company floats its existing shares on a public exchange and lets the market determine the price. Ahead of a debut planned for Sept. 30, Palantir’s bankers have told investors the shares could start trading around $10 apiece, according to people familiar with the matter. That equates to a market valuation of nearly $22 billion on a fully diluted basis.