Yes. If you’re using lets encrypt then note that they do not support wildcard certs with the HTTP-01 challenge type. You will need to use the DNS-01 challenge type. To utilize it you would need a domain registrar that supports api dns updates like cloudflare and then you can use the acme.sh package. Here is an example guide i found.
Note that you could still request multiple explicit subdomains in the same issue/renew commands so it’s not a huge deal either way but the wildcard will be more seamless in the future if you don’t know what other services you might want to selfhost.
Edit: i see now they’re talking about private IP, but in case you want to learn about getting a static IP for other things…
Many ISPs will give you a dynamic (changing) IP rather than a static (unchanging) IP. Just check your IP once a week for a few weeks to see if it changes.
There are some services that get around this by checking your ip regularly and updating their records automatically. This is called a dynamic DNS provider (DDNS). I used to use “noip” but since then there are quite a few like cloudflare DDNS.
Beyond that you just would want to make sure your router or whatever device is assigning IPs on your network to give a static assignment to the server. Assigning IPs is handled by a DHCP server and it would usually be your router, but if you have a pihole you might be using that as a DHCP server instead.
Between DDNS and DHCP you can make sure both your external IP and internal IP are static.