I can confirm the same error when trying to use the apt repository (apt.insync.io). DNS resolution shows no record for the domain:
$ dig apt.insync.io
; <<>> DiG 9.18.12-0ubuntu0.22.04.2-Ubuntu <<>> apt.insync.io
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 19660
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65494
;; QUESTION SECTION:
;apt.insync.io. IN A
;; Query time: 4 msec
;; SERVER: 127.0.0.53#53(127.0.0.53) (UDP)
;; WHEN: Tue Aug 08 17:30:13 -04 2023
;; MSG SIZE rcvd: 42
I spent 2 hours trying to debug an issue with my Ansible playbook because of this. As ssbroski reminds us yet again: