addons: Duck DNS: can't renew

The problem

Whenever addon tries to renew the certificate from Letsencryt it fails.

Environment

• Add-on with the issue: Duck DNS
• Add-on release with the issue: 1.12.4
• Last working add-on release (if known): no idea
• Operating environment (OS/Supervised): HassOS 4.15

Problem-relevant configuration

lets_encrypt:
  accept_terms: true
  certfile: fullchain.pem
  keyfile: privkey.pem
token: xxxxxxxxxxxxxxxxxxxxxxxxxx
domains:
  - xxxxxxx.duckdns.org
aliases: []
seconds: 300

Traceback/Error logs

addon logs:

[s6-init] making user provided files available at /var/run/s6/etc...exited 0.
[s6-init] ensuring user provided files have correct perms...exited 0.
[fix-attrs.d] applying ownership & permissions fixes...
[fix-attrs.d] done.
[cont-init.d] executing container initialization scripts...
[cont-init.d] done.
[services.d] starting services
[services.d] done.
# INFO: Using main config file /data/workdir/config
+ Account already registered!
[01:29:46] INFO: OK
2.83.208.156
NOCHANGE
# INFO: Using main config file /data/workdir/config
Processing xxxxxxxxxx.duckdns.org
 + Checking domain name(s) of existing cert... unchanged.
 + Checking expire date of existing cert...
 + Valid till Nov 13 23:25:36 2020 GMT Certificate will expire
(Less than 30 days). Renewing!
 + Signing domains...
 + Generating private key...
 + Generating signing request...
 + Requesting new certificate order from CA...
  + ERROR: An error occurred while sending head-request to https://acme-v02.api.letsencrypt.org/acme/new-nonce (Status 000)
Details:
ERROR: Problem connecting to server (post for https://acme-v02.api.letsencrypt.org/acme/new-order; curl returned with 7)

acme-v02.api.letsencrypt.org reachable from host:

➜  ~ dig acme-v02.api.letsencrypt.org         

; <<>> DiG 9.16.6 <<>> acme-v02.api.letsencrypt.org
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 11071
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
; COOKIE: e05a4e4198d98267 (echoed)
;; QUESTION SECTION:
;acme-v02.api.letsencrypt.org.	IN	A

;; ANSWER SECTION:
acme-v02.api.letsencrypt.org. 10 IN	CNAME	prod.api.letsencrypt.org.
prod.api.letsencrypt.org. 10	IN	CNAME	ca80a1adb12a4fbdac5ffcbc944e9a61.pacloudflare.com.
ca80a1adb12a4fbdac5ffcbc944e9a61.pacloudflare.com. 10 IN A 172.65.32.248

;; Query time: 20 msec
;; SERVER: 172.30.32.3#53(172.30.32.3)
;; WHEN: Sat Oct 31 02:12:05  2020
;; MSG SIZE  rcvd: 287

duckdns.org reachable from host:

➜  ~ dig duckdns.org                 

; <<>> DiG 9.16.6 <<>> duckdns.org
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 29814
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
; COOKIE: b03a4b52438c318e (echoed)
;; QUESTION SECTION:
;duckdns.org.			IN	A

;; ANSWER SECTION:
duckdns.org.		10	IN	A	44.230.159.203

;; Query time: 180 msec
;; SERVER: 172.30.32.3#53(172.30.32.3)
;; WHEN: Sat Oct 31 02:12:22  2020
;; MSG SIZE  rcvd: 79

Additional information

There is older reports and seems that the problem persists:

• https://github.com/home-assistant/hassio-addons/issues/549
• https://github.com/home-assistant/hassio-addons/issues/320