Look, there isn't one product that all painters know secretly as "the best primer" and that are "kept under their hats so that consumers won't find out about it". Each one has their favorites for sure but there are dozens of primers out there made for different situations.
If you want an idea of 6 of them, some of which we use, go to the Benjamin Moore website and look for the chart under 'Fresh Start' primers for an idea of what they recommend for different substrates.
I am sure the other manufacturers have the same, perhaps not on a website but somewhere.
In answer to your question, yes an alkyd primer is excellent on plaster...
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