OPDS is the standard for ebook distribution. Most eBook apps support it, I bet your boox does too.

You can subscribe to a feed and browse the catalogue and download a book. Some popular OPDS catalogues are:

• Feedbooks
• Internet Archive
• Manybook
• Project Gutenberg
• Standard Ebooks
• unglue.it

If you use Linux, check out Foliate reader from Flathub.

CasaOS is very easy to use and it’s a good starting option so you can test if self-hosting is for you. If you outgrow CasaOS, I can recommend an intermediate solution called: Coolify.

Fortunately linuxserver’s main hosting is no longer dockerhub.