There’s is no true friend that will ever feel threatened by your relationship. If they are, then go ahead and assume that there are some cards they failed to put on the table when your friendship began.
Maybe they’re threatened at the possibility that you’ll have less time for them. This is a true fact because of course, you’ll be spending more time with the person you’re trying to build a lifetime with. Insecurities can get ugly but that’s their problem, not yours.
On a final note
Just before you do something silly like put your friend before your partner, I am pretty certain that when they get into their own relationship, they won’t even thing twice before putting their partner before you. And there is nothing wrong with that!