DSD: DoP versus native, and what your streamer supports
Serento sends DSD the way your renderer says it wants it, and never converts.
Serento plays DSD up to DSD512, either wrapped in PCM frames (DoP v1.1) or natively, depending on what the renderer advertises. It never converts DSD to PCM to make it play.
Which one you get is the renderer's decision, not a setting: at connection time Serento reads the device's declared capabilities and uses native DSD when the device announces it, DoP otherwise.
Seeking within a DSD track is not universally supported. Some renderers, Rockna's among them, accept a DSD stream happily but reject or ignore a seek request inside it. That is a limitation of the device's firmware, not something Serento can work around, because there is no way to seek a DSD stream except by asking the renderer to.
If a DSD album shows its format badge without a rate, the server did not report a trustworthy sample rate for it. Serento probes the file header to recover the real rate rather than displaying one it does not trust.
Still stuck
Write to us with your server, your streamer and what you expected to happen. If you can, send the diagnostic log from Settings, it usually answers the question faster than a description can.