The Super Butte/Big Sky route, just outside of Big Sky has some closures until sometime in July due to a bridge being replaced.
The easiest alternate imo is asbestos ridge rail to moose creek to the gallatin crest. Honestly this would be better than taking deer to portal and having to walk a narrow windy section of 191. If you went moose creek to swan creek you could go over Hyalite peak and see Hyalite canyon which gives glacier a run for its money. This would be a few miles more than just blasting up portal creek to the crest but IMO worth it. Water is tough on the crest so be aware”
The problem people are facing on the Onion route is they can get to Ennis and then to Big Sky going SOBO but when they reach 191 where the Deer Creek Trail takes them across the Gallatin River on Markley Bridge, the bridge and trail are closed.
The river is very high and cannot be safely forded.
Trail is anticipated being reopened late July according to the Bozeman Ranger Station (called June 1).
So SOBOs need an alternative route to continue on the way to Gardner, currently a 61 mile stretch.
And
https://caltopo.com/find “cdt/alternates.html Brian and Martina’s Route: http://www.wildernesstravels.co.uk/cdt/bigsky.htm@