Having already configured a VLC-powered Google TV configuration with USB hard drives for a relative without the router or download speed needed for reliable streaming, I'm now trying to configure a similar setup for another relative with a non-smart TV and an even slower download speed.
The only requirements for such a device would be the ability to be controlled entirely with a remote, a USB-A or USB-C port compatible with USB hubs and media storage devices, and the reliable playback of videos of assorted codecs and file extensions. As Roku, FireTV, and Android/Google TV streaming sticks tend to be plastered with ads as a means of promoting content within their ecosystems, an alternative HDMI device that minimizes the number of button presses between turning on the TV and and reaching the navigation menu for videos on attached USB storage devices would be preferred.
The "simplest" method is to plug the USB straight into the TV if the TV supports USB playback. You could also try plugging the USB into the router as many of them support DLNA servers - not a solution but a piece of the puzzle that can be used.