Silicone grease is often used on O-rings. That is what Andrew (now Commscope) packaged with their connectors for high powered coax called Heliax. I never bought any silicone grease because I’ve always had some left over. Silicone based O-ring grease is available from Lowe’s.
https://www.lowes.com/pd/aqua-ez-o-r...iABEgK3APD_BwE