Is a condom still SOP for covering the muzzle of weapon to protect from water incursion?
No, quite a while back the US military introduced purpose made covers.
https://www.joesarmynavyonline.com/6-Pack-GI-AR-15-M16-Muzzle-Cover-p/215364-6.htm
“Actual US GI M16/AR15 plastic muzzle covers fits snugly over most standard AR muzzles. Helps to protect the bore from mud and dust. Brand new. NSN 5340-00-880-7666. Original packaging is dated 06-11 and says: CAP, PROTECTIVE, DUST “