Keith, mobility can be a tricky topic: because everyone is put together a little differently, each athlete will need pick and choose what they need to work on more. We did have a general mobility session in our first BMTG program, focusing on hips, shoulders, thoracic spine, and hamstrings (single leg on a door frame).
For general strength training and specific steep hill climbing, try to have adequate mobility at the ankles, hips, thoracic spine, and shoulders. Also make sure that you are addressing hamstring flexibility.
Because of larger step ups, step downs and squats, ankle mobility is really important. Foam-rolling / SMR of the calf and potentially the achilles will be a good start. Half-kneeling mobilizations are great. You can add in heavy bands to improve glide in the ankle. Don’t preoccupy your time with dozens of mobility drills, just try a few. If you notice a big difference from one side to the other, spend your energy on the side that needs catch-up.
“Hip openers” is used generically, but many concepts are great. UA Yoga is great for this in the evening. For more active versions, you can use frog patterns, dynamic planks, lunge patterns, and “worlds greatest stretch” variations. For controlling this mobility, Cham Mtn Fit can’t be beat.
The term “shoulder openers” is also widely used, but many versions are great. Restricted shoulders can really affect gait, and poor mobility can even be the cause of poor squat mechanics. Scott put out this video a while back: https://www.youtube.com/watch?v=aFjx74PzghA. If you find some restriction in any of those patterns, often times some SMR can help. The Roll Model is a really helpful tool to scan and identify areas to focus on with SMR. There are also some ways to improve mobility with traction, but try the other routes first.
UA Yoga has a great thoracic spine mobilization in Module 2. Side-laying, bent knees.
For a simple routine to follow-along, here’s one in-house video: https://www.youtube.com/watch?v=ixm3Bj239eU
To try to retain improved mobility, you’ll want to perform a pattern or patterns that will load that joint. Alternatively, if you do some mobility in the late evening, you’ll be following up with a night of rest where hopefully you aren’t doing anything to undo your work (slouching in a chair, hunching over a computer, etc.). Using UA Yoga in this manner is great.