Managed DNS provider
Cloudflare's Learning Center: Resources on cyber-security and how the Internet works
I want to try switching to deSEC which is "a free DNS hosting service, designed with security in mind. Running on open-source software and supported by SSE, deSEC is free for everyone to use."
Cloudflare's security features (e.g., HSTS) are useful since I can't set HTTP headers on GitLab Pages -- although I do use <meta> elements where possible. My web hosting service is something I should consider changing.
Domain name registrar
I have two domain names registered with Porkbun
Email (mailbox.org)
Knowledge base: Using a custom domain (SPF, DKIM, and DMARC)
Knowledge base: Using the Jabber service with a custom domain