I would suggest the Tamron 17-28mm f/2.8 Di III RXD for those Utah landscapes. You might want to consider how narrow 20mm feels when you are at the bottom of a canyon looking up. Be careful with lens swaps in the desert dust tho. While the Tamron 20-40mm f/2.8 Di III VXD is more versatile, the extra width on the 17-28mm is much safer for those massive views.

Coming back to this after looking at some MTF charts... honestly I was kinda let down by the Tamron 20-40mm f/2.8 Di III VXD for pure landscape work. It is a great walk-around lens but the corner resolution unfortunately falls off way more than I expected compared to the older glass. I had some annoying issues with chromatic aberration on high-contrast canyon edges too which was a pain to edit out. I took the Tamron 17-28mm f/2.8 Di III RXD to Zion last year and even tho the range is tiny, 17mm is basically mandatory when you are deep in those canyons. 20mm just feels too cramped when you are trying to capture the scale of the Great White Throne from the valley floor. Quick tips:

• Stick to lenses with 67mm filter threads so you can swap a single B+W 67mm Master Circular Polarizer between them easily.
• Bring a rocket blower for the sensor because that Utah dust gets everywhere the second you swap lenses.

I've spent way too much time looking at distortion graphs and MTF charts lately, and honestly, if you're worried about that range gap, you might want to consider the Tamron 17-50mm f/4 Di III VXD instead. It covers everything you're looking for without the constant lens swapping. I know it's an f/4 lens, but for landscapes in Zion, you’re gonna be stopped down to f/8 or f/11 most of the time anyway to keep those canyon walls sharp from front to back. I remember my first trip to the Southwest with a fast prime and I ended up missing so many shots because I was too busy swapping glass in a windstorm. The dust there is no joke and will absolutely get onto your sensor if you aren't careful. Just a heads up tho, make sure to consider that the f/4 might struggle if you plan on doing any astro at night in Bryce. The light gathering just isnt the same as an f/2.8. But for pure landscape, the internal zoom design of that 17-50mm is a huge plus for weather sealing. Since your budget is tight, I’d suggest looking for a Haida M10 Filter Holder with a drop-in ND filter later on. It really helps with those long exposures at the Virgin River. Just take it slow and dont stress too much, the a7IV is a beast and you'll get some killer shots regardless of which one you pick.