The other poster gave you a lot. If that’s too much at once, the really low hanging fruit you want to start with is:

• Choose an active, secure distro. There’s a lot of flavors of Linux out there and they can be fun to try but if you’re putting something up publicly it should be running on one that’s well maintained and known for security. CentOS and Debian are excellent easy choices for example.

• Similarly, pick well maintained software with a track record. Nginx and Apache have been around forever and have excellent track records, for example, both for being secure and fixing flaws quickly.

• If you use Docker, once again keep an eye out for things that are actively maintained. If you decide to use Nginx, there will be five million containers to choose from. DockerHub gives you the tools to make this determination: Download number is a decent proxy for “how many people are using this” and the list of updates tells you how often and how recently it’s being updated.

• Finally, definitely do look at the other poster’s notes about SSH. 5 seconds after you put up an SSH server, you’ll be getting hit with rogue login attempts.

• Definitely get a password manager, and it’s not just one password per server but one password per service. Your login password to the computer is different from your login to any other things your server is running.

The rest requires research, but these steps will protect you from the most common threats pretty effectively. The world is full of bots poking at every service they can find, so keeping them out is crucial. You won’t be protected from a dedicated, knowledgeable attacker until you do the rest of what the other poster said, and then some, so try not to make too many enemies.

Paranoid external security. I’m assuming you already have a domain name. I’m also assuming you have some ICANN anonymization setup.

This is your local reverse Proxy. You can manage all this with a container called nginx proxy manager, but it could benefit you to know it’s inner workings first. https://www.howtogeek.com/devops/what-is-a-reverse-proxy-and-how-does-it-work/

https://cloud9sc.com/nginx-proxy-manager-hardening/

https://github.com/NginxProxyManager/nginx-proxy-manager

Next you’ll want to proxy your IP address as you don’t want that pointing to your home address

https://developers.cloudflare.com/learning-paths/get-started-free/onboarding/proxy-dns-records/

Remote access is next. I would suggest setting up wireguard on a machine that’s not your webserver, but you can also set that up in a container as well. Either way you’ll need to punch another hole in your router to point to your wire guard bastion host on your local network. It has many clients for windows and linux and android and IOS

https://github.com/angristan/wireguard-install

https://www.wireguard.com/quickstart/

https://github.com/linuxserver/docker-wireguard

Now internally, I’m assuming you’re using Linux. In that case I’d suggest securing your ssh on all machines that you log into. On the machines you’re running you should also install fail2ban, UFW, git, and some monitoring if you have the overhead but the monitoring part is outside of the purview of this comment. If you’re using UFW your very first command should be sudo ufw allow ssh

https://www.howtogeek.com/443156/the-best-ways-to-secure-your-ssh-server/

https://github.com/fail2ban/fail2ban

https://www.digitalocean.com/community/tutorials/ufw-essentials-common-firewall-rules-and-commands

Now for securing internal linux harden the kernel and remove root user. If you do this you should have a password manager setup. keepassx or bitwarden are ones I like. If those suck I’m sure someone will suggest something better. The password manager will have the root password for all of your Linux machines and they should be different passwords.

https://www.makeuseof.com/ways-improve-linux-user-account-security/

https://bitwarden.com/help/self-host-an-organization/

https://keepass.info/

Finally you can harden the kernel

https://codezup.com/the-ultimate-guide-to-hardening-your-linux-system-with-kernel-parameters/

TLDR: it takes research but a good place to start is here

https://www.digitalocean.com/community/tutorials/recommended-security-measures-to-protect-your-servers