The certificate is NOT trusted. The certificate issuer is unknown

Hello everyone,

I am working with the Siemens IoT2050 gateway equipped with a LoRaWAN concentrator MPCIE card. The goal is to deploy the Chirpstack private network but when I want to add the Chirpstack repository I get this certificate error:

Ign:12 Index of /packages/3.x/deb/ stable/main arm64 Packages
Ign:13 Index of /packages/3.x/deb/ stable/main Translation-en
Ign:14 Index of /packages/3.x/deb/ stable/main Translation-en_US
Ign:11 Index of /packages/3.x/deb/ stable/main all Packages
Ign:12 Index of /packages/3.x/deb/ stable/main arm64 Packages
Ign:13 Index of /packages/3.x/deb/ stable/main Translation-en
Ign:14 Index of /packages/3.x/deb/ stable/main Translation-en_US
Ign:11 Index of /packages/3.x/deb/ stable/main all Packages
Ign:12 Index of /packages/3.x/deb/ stable/main arm64 Packages
Ign:13 Index of /packages/3.x/deb/ stable/main Translation-en
Ign:14 Index of /packages/3.x/deb/ stable/main Translation-en_US
Ign:11 Index of /packages/3.x/deb/ stable/main all Packages
Ign:12 Index of /packages/3.x/deb/ stable/main arm64 Packages
Ign:13 Index of /packages/3.x/deb/ stable/main Translation-en
Ign:14 Index of /packages/3.x/deb/ stable/main Translation-en_US
Ign:11 Index of /packages/3.x/deb/ stable/main all Packages
Err:12 Index of /packages/3.x/deb/ stable/main arm64 Packages
Certificate verification failed: The certificate is NOT trusted. The certificate issuer is unknown. Could not handshake: Error in the certificate verification. [IP: 188.166.134.65 443]
Ign:13 Index of /packages/3.x/deb/ stable/main Translation-en
Ign:14 Index of /packages/3.x/deb/ stable/main Translation-en_US
Reading package lists… Done
E: Failed to fetch https://artifacts.chirpstack.io/packages/3.x/deb/dists/stable/main/binary-arm64/Packages Certificate verification failed: The certificate is NOT trusted. The certificate issuer is unknown. Could not handshake: Error in the certificate verification. [IP: 188.166.134.65 443]
E: Some index files failed to download. They have been ignored, or old ones used instead.

I’ve already checked the clock, versions, etc., but I don’t see where the problem comes from.
If anyone can help with any information I would be very grateful

The problem is probably an outdated Letsencrypt root certificate on the system. Please see: letsencrypt root certificate expired - Google Zoeken.