I agree with the last few posts about Ipad. If OP had not ruled it out, it would be a strong option. Specifically in the mid priced 10" tablet category, there is no better all-around tablet and bang for the buck purchase than a current Ipad 9.7 with 128GB storage. I see these for $329 in US.

I researched these recently, also played with my brother's and with the new 2018 version at Best Buy. Extremely tempted, it's hands down the best tablet hardware-wise and user experience-wise that one can get in this under $400 price range. In fact if my forthcoming S5e doesn't pan out for whatever reason, I'll throw in the towel and get the Ipad.

OP, I assume from your post that you have other reasons for avoiding Apple, such that the inherent value of the Ipad, the slick iOS user experience, and their vast app store, are not your main considerations.

That's the case for me; I have other reasons for preferring to stay all Android as my mobile OS, including easy sharing of apps and data, with my Samsung Galaxy S10 phone. And leveraging my existing, deeper experience level with Android OS and ecosystem. And the fact Android is more 'open' than Apple's ecosystem, which is really important to me. Finally, the galaxy is my favorite phone design of all time and it's unlikely I'll abandon it soon, another reason to stick with Android. In short, I don't need the best available tablet in existence. For the fairly modest uses I'll have for this tablet, like content consumption, web browsing, and streaming audio and video, all I need is a tablet with a nice high-res display, adequate storage and CPU, and full compatibility with Android 9. The S5e and some of the Huawei Mediapad M5 offerings are the best ones I've found that would do the job at this price point.