Question before I get my kindle

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Hello everyone, before I make my first ever kindle purchase I want to be 100% sure that if I got a kindle device only for books that I download from website like Anna's archives and z-liberary will work fine (epub & or pdfs... ETC) , or my books will be removed by Amazon cause I got them for free not purchased from their storefront?

Cause if that would be the case I better be on my iPad or iPhone for reading my books

So I'll be only using it for reading downloaded books as I mentioned

By the way all of those books I sent them via send to kindle email and they appeared just fine on kindle app on my phone and iPad

Thanks in advance for all your help