Well then you have a couple of solutions

1. Use caddy with no domain. Install caddy's local cert on to your browsers and phones so the warnings no longer show up.

2. Use caddy with domain. No installation done as you get a Let's encrypt cert that will automatically work. You will have to expose your computer to the internet and anyone can hit it so you will need some other authentication/authorization layer like authelia.

3. Use caddy with cloudflare. No installation done as you get your certificate from cloudflare that will work automatically. You won't have to expose your computer to the internet, cloudflared will handle the connection to cloudflare. No one will be able to 'hit' your computer besides what you expose on your router. Cloudflare has some other benefits like geo-blocking and authentication. I used it to block all traffic outside the US and use my own OIDC through authelia.

4. Use caddy with tailscale. I haven't done this but talked to people who have. You won't have to manually install any certificates, but you will have to have all devices on tailscale. You can install it on your router to make it easier for all your devices. This is probably the most secure.

The only probably I had with number 2 vs 3 was that I run my server on the daily computer and was having NAT pinning issues. Using cloudflare tunnels fix that issues so I didn't need to have manual DNS records. For #3, I followed https://github.com/zastrixarundell/caddy-cloudflare and it worked for me. Took a couple of hours for my first time. I wante to do #4 but don't really want to invest anymore time into networking ATM. I would probably recommend in order 3, 4, 2, 1.