Last I heard, Amazon had locked down the approach for side-loading Fully Kiosk Browser in early 2023 (disabling the ‘Files’ app which is white-listed for performing installs).
I had already installed Fully Kiosk on mine before they blocked it. There’s some hope that the European Digital Markets Act (DMA) which should force Apple to allow people to side-load apps would also apply to Amazon’s devices, but I suppose time will tell on that front.
The newest versions are much better than their older counterparts, but I would warn that the Amazon Fire tablet is the cost effective approach – not necessarily the smoothest experience. I’ve seen several community members move to high end Android tablets or iPads when they were seeking better performance and they seemed satisfied with the improvement.
While the underlying hardware is a critical factor, another factor is that Amazon bundles their WebView and OS together, so if they stop updating the older device, you end up with an older WebView that isn’t as performant (on top of the hardware not being as good a newer models).
I guess I will have to put off the Echo Show 15 for now.
BTW, I just found out that Amazon is giving away a promotional credit for signing up for their Amazon Business account. The perfect timing to have on top of their Prime sale. With this price point in mind, I think I’ll grab this newer HD 10 a try.