Adding my two cents because I did a similar trip! I was torn between these:

• Canon RF 24-105mm f/4L IS USM: Fantastic L-series glass. Super sharp. Might lack reach for wildlife tho.
• Canon RF 24-240mm f/4-6.3 IS USM: Amazing versatility. Great for landscapes and distant animals, just a bit slower. I grabbed the 24-105. Loved those crisp mountain shots! It's a total workhorse.

Honestly, since you just dropped a lot of cash on that R5 Mark II, you really want to stick with native glass to take advantage of the faster data throughput and the extra pins on the mount. EF lenses work fine with an adapter, but the RF system is basically built for the high-bandwidth needs of that 45MP sensor and its fast burst rates. For a trip to Montana, you definitely want something versatile. I have been using the Canon RF 24-105mm f/4L IS USM for most of my travel work and I am very satisfied with the results. It is a professional-grade workhorse that handles everything from wide landscapes to tighter portraits. The constant f/4 aperture is great, and the Nano USM motors provide nearly silent, instant autofocus which is perfect for the R5 II subject tracking. The edge-to-edge sharpness is solid for a zoom, and the 5-stop optical image stabilization works in tandem with your cameras IBIS to give you incredible stability for handheld shots. One quick tip for your trip: if you think youll be shooting distant wildlife and dont mind losing a bit of low-light performance, the Canon RF 24-240mm f/4-6.3 IS USM offers more reach, but the L-series 24-105 has much better weather sealing and build quality. Given your 1500 budget, the 24-105 fits perfectly and leaves you some room for extra batteries or a fast memory card like the Lexar Professional CFexpress Type B Gold Series 128GB. Stick with native RF glass so you dont have to mess with bulky adapters while hiking... its just way more streamlined.

Huh interesting. I had no idea. The more you know I guess 🤷