https://motherfuckingwebsite.com/ If it’s just text, you can probably make a static HTML website and accomplish your goals. I’m not sure what format it’s in now but Markdown is what I use and then just export to HTML.

If you just want to host epub (or equivalent files), you can still make a static page and link to them with Cloudflare Pages, GitHub.io, or one of many free static page hosting sites.

Is it transactional emails, one-to-many, or like a message board where people get email notifications? I’m not sure I’ll have a good answer but I suspect that context would change some answers.

I don’t self-host Nextcloud. I have a cheap cloud instance running it and it’s essentially my off-site backup for important documents. I don’t put just anything up there but I live in New Orleans so I feel like I should assume my home server won’t necessarily be online when I most need insurance documents and shit like that.