I would say it depends on the type of salvia. Nemerosa types such as Caradonna can cope with "light" shade, although it might be better if it gets some sun for a short while. Shrubby salvias such as Hot Lips are better in full sun and well drained soil
I have several shrubby salvias in pots against the west-facing front wall of my house, so they only get sun in the afternoon/evening, and they do fine. I also have a few in the back garden which only get the sun in the morning. It seems to be enough for them. They don't do noticeably differently from the ones that get sun for longer.
Doncaster, South Yorkshire. Soil type: sandy, well-drained
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Shrubby salvias such as Hot Lips are better in full sun and well drained soil