I'm a big fan of ghost (especially for anyone into self-hosting!), but the lack of a free plan makes it harder to use as my default recommendation. (Also the lack of single opt-in signup is a deal breaker for me personally, though I understand many people don't care/prefer double opt-in anyway.)

I think https://beehiiv.com is another good alternative, though the styling isn't as nice as on ghost, and I personally found the editor to be glitchy and infuriating to use. Maybe it's just a problem on Firefox. I'd probably use that as my own recommendation for anyone looking for a newsletter platform and cross my fingers that they have better luck with the editor :).