I've been using one of the Kobo Clara devices running Plato (built in Rust) for a few years now. Other than a couple of minor bugs early on, I've had no issues.

It's largely the exact device that I want my book reader to be:

* Small and lightweight

* Nice epaper screen

* No need for an internet connection whatsoever

* Natively understands EPUB

* Just reads books -- no ads, no markets, no apps, no upsell

The built-in Kobo firmware isn't great. IIRC Rakuten/Walmart hoover up and sell your reading habits, etc. Hence one reason why I don't connect mine to the internet (running Plato probably fixes this, but restarting the device doesn't immediately go into Plato). The device is also weirdly sluggish with the default Kobo software, and much faster in Plato.