I wonder sometimes if the advice against pointing DNS records to your own residential IP amounts to a big scare. Like you say, if it’s just a static page served on an up to date and minimal web server, there’s less leverage for an attacker to abuse.

That advice is a bit old-fashioned in my opinion. There are many tools nowadays that will get you a very secure setup without much effort:

• Using a reverse proxy with automatic SSL certs like Caddy.
• Sandboxing services with Podman.
• Mitigating DoS attacks by using a WAF such as Bunkerweb.

And of course, besides all these tools, the simplest way of securing public services is to keep them updated.

I’ve found that ISPs too often block port 80 and 443. Did you luck out with a decent one?

Rogers has been my ISP for several years and have no issue receiving HTTP/S traffic. The only issue, like with most providers, is that they block port 25 (SMTP). It's the only thing keeping me from self-hosting my own email server and have to rely on a VPS.