JEDII Tech is hosted using Ghost, an open source publishing platform. I chose Ghost because I've used Wordpress for years and want to try something different (and I'd really prefer to avoid the white male-dominated, YCombinator-funded Substack world). JEDII Tech is currently self-hosted (on a $5/month Digital Ocean droplet) so that I can get a feel for what it's like, although I may well switch to Ghost's hosting at some point.
JEDII News currently uses a modified version of the Attila theme, created by Peter Amende. I chose this theme because Marco Zehe uses it for Marco's Accessibility Blog, and he says the author (as well as the broader Ghost community) takes accessibility seriously. I tweaked the theme to pin featured posts using the approach described here by Julian Barog (although had to adapt it for the Attila theme).
For mail, we use mailgun because that's what Ghost newsletters support.