(I'm not an expert with this sort of stuff, so forgive me for any wrong terminology etc.)
For reference, here's what it is, 6th and final generation specifically.
Basically we mainly use it to expand the wifi coverage on the property, since it acts as a wifi hotspot and allows us to create a 2nd network/connection for us all to use and in addition to our original modem/router.
It's been on the fritz lately, was discontinued several years ago, and it doesn't seem like there's anything exactly like it anymore. Any suggestions? Ideally something cheap and easy to set up.
OpenWRT is an open-source router firmware that can be installed on (most) consumer routers to add a wireless network that extends your existing network. It's a bit complicated to set up and install, though. But if you have an old router that is compatible you could follow a couple tutorials to get it working in a pinch.
Asus routers, especially when the open-source Asus Merlin is installed (much easier to install than OpenWRT and looks and functions the same as stock firmware, but with added features) can have this functionality. I think TP-Link routers can as well, and they make wireless repeaters that are very cheap and work fine.