How can I access my own ebooks?

Good day everyone,

I'm being denied access to my ebooks by my provider, which is Tolino.

Back then I chose Tolino because it offered many means to access my books without having to bring along a bookshelf everyhwhere I went. Unfortunately it escaped my attention that Tolino was acquired by - drumroll - Roku. Since then it seems they enshittified the android app. As long as my device is connected to a VPN the app says "no internet connection" and won't let me access anything. As soon as I disable my VPN it works normally. Yeah, that's unacceptable.

Do you guys know a way to pull my books?

Further, can you recommend me fair ebook provider? Google Books apparently works, but for one Google is known to shut down popular services without further notice and, well, it's Google.

zlibrary isn't really an option, because it doesn't have the works I'd like to read in my preferred language.