In terms of blogs, for selfhosting comments, the main ones that seems interesting for selfhosted setups are probably remark42[0] and utterance.es[1]. Remark42 is a low barrier Disqus clone with social logins (as well as just plain usernames) that also makes it fairly easy for users to bulk export their own data (as well as delete I think?), which ought to take care of most GDPR stuff.
Utterance.es is GitHub issues backed comments, which is an inherent barrier to commenting, but YMMV if that's an actual problem (generally the value of unbarred comment sections is abysmal). Like remark42, it's open source, but you're relying on a third party's servers.
[0]: https://github.com/umputun/remark42
[1]: https://utteranc.es/