I know you asked specifically about mailing lists, then most answers, including mine below, are more newsletters, but if you want a mailing-list type feel, there are also Patreon, Reddit, individual blogs, and other communities that communicate in much the same way and have the same sort of interesting mailing-list feel, with similar volumes. Not sure how much you'd considered those, but a lot of the Reddits I'm in would have been mailing lists/usenet topics pre-Reddit,

Even some public Slack and Discord servers have the same mailing-list feel. eg. I'm in the monitoring.love Slack with a monitoring/SRE focus, and the r9y.dev Discord which is Reliability/SRE/Monitoring focused, and both have the same mailing list type feel.

Consider the Handmade conference newsletter [0]. We're an indie conference focused on low-level programming (nuts and bolts kind of thing) and we occasionally send interesting emails on these topics. Of course we also announce ticket sales and all that, but sparingly :)

[0] https://handmade-seattle.com/newsletter

Indeed, that's mostly why I was asking. Mailing lists would be a bit more novel topic.