Make sure to consider how much those 12-24mm filters cost, it's kinda scary... I'd suggest the Sony FE 16-35mm f/2.8 GM II because it's way more practical for your trip.

Just seeing this now... I've been using the Sony FE 16-35mm f/2.8 GM II on my a7R V for a while and I'm really happy with how it handles. Since you're heading to Iceland, 16mm is usually plenty wide for those massive landscapes. Plus, it takes standard 82mm screw-in filters, which is a huge deal when you're dealing with the wind and spray near waterfalls. I use the Hoya 82mm NXT Plus Circular Polarizer and it works perfectly without any of the bulk of those 12-24mm systems. If you want to stay under budget and still get incredible sharpness, the Sony FE 20mm f/1.8 G is also a fantastic shout. It's light, way cheaper, and honestly looks stunning on that high-res sensor. I have no complaints using it for astro too. But for a one-lens trip, the 16-35 GM II is just more versatile. It's a beast.

Saw this earlier but just now responding... unfortunately the Sony FE 12-24mm f/2.8 GM has some pretty disappointing vignetting and barrel distortion at 12mm that really messes with the raw data. I dont think its worth it. Ngl I expected better. Based on the MTF charts, the Sony FE 16-35mm f/2.8 GM II is way sharper. If you need super wide, the Sony FE 14mm f/1.8 GM actually measures better for distortion. Lemme know if you need more data.