My issue is very similar to this thread. Ubuntu image provided by AWS is not running with NetworkManager. The network renderer is networkd and dns works with the systemd-resolved.
It looks like the sdwan0 is never coming up or name resolution is somehow broken.
I tried with and without headless auth.
The client seem to be stuck in a loop with these events:
[WARNING] [libsdwan][6300] http::request::handle_response: GET "https://MYDOMAIN.twingate.com/api/v1/public_keys" failed - dns error: -4 (non-recoverable failure in name resolution), socket error: 11 (Resource temporarily unavailable), tls error: 0 ((null))
[WARNING] [libsdwan][6300] operator(): failed HTTP request 8971431708067700984 -1 dns error: non-recoverable failure in name resolution
[WARNING] [libsdwan][6300] [controller] operator(): failed to get public keys: dns error: non-recoverable failure in name resolution, code -1
[INFO] [libsdwan][6300] sdwan_state: Error None
[INFO] [client] [6300] State: 'Error', client mode: 'None'
[WARNING] [client] [6300] No DNS servers found for bypass interface "eth0"
[INFO] [client] [6300] Using DNS servers: '1.1.1.1, 8.8.8.8, '
[INFO] [libsdwan][6300] set_dns: 1.1.1.1 8.8.8.8
[INFO] [libsdwan][6300] sdwan_state: Offline None
[INFO] [client] [6300] State: 'Offline', client mode: 'None'
[INFO] [libsdwan][6300] sdwan_state: Authenticating None
[INFO] [client] [6300] State: 'Authenticating', client mode: 'None'
[msg] Nameserver 8.8.8.8:53 has failed: request timed out.
[msg] Nameserver 1.1.1.1:53 has failed: request timed out.
[msg] All nameservers have failed
Despite the timeout error from name server 8.8.8.8 and 1.1.1.1, name resolution seems to work (with dig command)