I've had Sony FE 24-70mm f/2.8 GM II on my Sony A6400 for for the last 6 months. The build quality is really solid, on top of that works great with Sony A6400. Can't really complain about anything.

Have you checked if Sony A6400 has any specific compatibility requirements?

So I've been using Sony FE 16-35mm f/2 (released this year).8 GM with my Sony A6400 for about 3 months. Based on my use, setup was easy, and easy to use with Sony A6400. No complaints so far.

After some research, I went with Sony FE 50mm f/1.2 GM for my Sony A6400. Frankly, quality is impressive. another plus complements Sony A6400 nicely. No regrets at all.

I've had Sony FE 70-200mm f/2.8 GM OSS II on my Sony A6400 for over a year now. In my testing, it's practical, furthermore easy to use with Sony A6400. It's been great so far.

After some research, I went with Sony FE 70-200mm f/2.8 GM OSS II for my Sony A6400. In my case, it's been very reliable, not to mention suits Sony A6400 well. Very happy with the choice.

Yeah, I definitely agree with the general vibe here that investing in quality glass is the way to go for the A6400. From a professional standpoint though, your going to want to look at the industry standards for weather sealing before committing. Basically, ngl, the biggest thing the community reviews always flag is how much dust can get into lenses that extend while zooming. Afaik, a lens with internal focal movement is way more reliable for long-term travel and protects the sensor better. Tbh, most pros in the forums suggest checking the gasket thickness on the mount too, just to be safe. TL;DR: Reliability is key—prioritize weather sealing and internal zooming to avoid sensor dust issues while on the road.

Any updates on this?

Are you planning any other gear? That could affect your travel lens choice for Sony A6400.