Are e-books harmful at bedtime?

I hear again and again that one should not use a mobile phone, PC or laptop before going to bed and one should not watch TV because the blue light would disturb the sleep. Is that the same with e-books? And are e-books bad for the eyes? My parents keep saying that cell phones damage your eyes permanently. If that's true, does that apply to e-books as well?

For e-books on the phone I recommend anyway no white background, but this sepia (can be in any app I know).

A blue light filter makes virtually nothing else. Black on sepia will not keep you awake or damage your eyes.

E-book readers are affected only with activated backlight.

E-book readers have a different kind of screen (e-ink), which needs at least during the day no built-in lighting, and does not light itself. I do not think that the switchable lighting has such a high proportion of blue. In many other devices you can also regulate the hue, or let automatically regulate with apps / programs depending on the time of day.

During the day, e-book readers are not lit and at night you can read them, if you want, even with an external reading light.
With my tolino, however, I can adjust the light temperature manually (or let it adjust automatically) so that the light changes from pretty blue to very yellowish. Continuously. That is very pleasant.

Not only with many other devices!
There are also ebook readers with Smartlight => blue light reduction.

Proper ebook readers are basically much more eye-friendly than cell phones or tablets!

And there are even ebook readers with Smartlight, so with blue light reduction! E.g.:
Tolino Shine 3,
Tolino 4HD,
Pocketbook Touch HD2,
Pocketbook Touch HD3

These ebook readers are absolutely recommended.
With those you can also use the onleihe the city libraries, so eBooks rent online for free online, download and read - if you have a library card.