Quickly dropping in while I have a sec. Honestly, for 700 bucks on an R5, you actually have some solid native glass options that wont break the bank. You dont need to mess with adapters if you dont want to.

• Canon RF 16mm f/2.8 STM is basically the cheapest way to get that ultra-wide look. Its tiny, weighs nothing, and runs about 300 bucks. Great for those massive mountain vistas.
• Canon RF 15-30mm f/4.5-6.3 IS STM gives you more zoom range for around 550. It has image stabilization which is nice for handheld landscape shots if you lose the light. The 16mm prime is sharp enough but has some heavy vignetting and distortion that the camera software fixes automatically. If you can find one, a used Canon EF 16-35mm f/4L IS USM with a Canon Mount Adapter EF-EOS R is technically superior glass, but its much heavier. For a Utah trip, that 16mm prime is honestly hard to beat for the price and portability tho.

Unfortunately, new lenses for the R5 are expensive. I think you'll need an adapter for older ones, but I had issues with that being bulky and not as good as expected, tbh.