turtle neck pullover stitch possibilities

I would like to knit an adult pullover with a turtle neck, have never knitted this type of pullover before. Have found patterns with a ribbed turtle neck , is it possible to knit the whole garment including the neckline in stocking stitch? I assume that stocking (stockinette) st. may not be firm enough to hold the neckline upright. I don,t want it to fold over.

Welcome to KnittingHelp!
Stockinette has a strong tendency to curl. That’s what would happen to a turtleneck knit in stockinette. You might be able to knit a long collar in stockinette and then double over the collar to the inside but you’d have to play around with it to get the look you want. Turtleneck jerseys without ribbing are even doubled over twice.
Ribbing gives shape and elasticity to the turtleneck and so it’s better adapted to that style.

Thank you so much, when all the patterns I looked at showed the ribbed neckline I thought there must be a reason for it.