Hi @fstriley,
If you don't mind to change the domain there are alternatives.
You can buy a cheap domain or get a free domain at http://www.freenom.com and use a dns provider like Cloudflare, it is free and has an API to update/create/delete DNS records and also allows to update records using ddclient to modify the records for your domain with your dynamic ip address.
If you don't like that idea, you can also use another free dynamic DNS provider that supports adding TXT records (needed for dns challenge) like https://www.dynu.com/. A few days ago I wrote a post with several steps to use this DDNS provider and acme.sh client.
These are the steps to use dynu.com:
1.- Create a free account on dynu.com.
2.- Create a Dynamic DNS Service on dynu.com. Here you add your subdomain and choose the base domain (there are a few to choose, in this example I will use mydyndomain as subdomain and dynu.net as base domain)
3.- Once the domain is created, go to Control Panel -> API Credentials and click on button Reset Credentials, now take note of Client ID and Secret (we will use them later).
4.- Here you could install their dynamic client so it will update your dynamic address or use wget, etc. more info here IP Update Client | Free Dynamic DNS Service | Dynu
5.- Install acme.sh client (more info in https://acme.sh)
curl https://get.acme.sh | sh
6.- Once installed, issue the cert for your domain. Here we will export 2 variables containing the previously created Client ID and Secret (obvously you need to replace the content of these variables with the real data):
export Dynu_ClientId="xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
export Dynu_Secret="yyyyyyyyyyyyyyyyyyyyyyyyy"
acme.sh --issue --dns dns_dynu -d mydyndomain.dynu.netAnd if all work as expected, you get your certificate.
Good luck,
sahsanu