I wrote all articles about this problem. But same result.
Output:
sudo apt update
Hit:1 http://tr.archive.ubuntu.com/ubuntu jammy InRelease
Get:2 http://tr.archive.ubuntu.com/ubuntu jammy-updates InRelease [119 kB]
Get:3 http://tr.archive.ubuntu.com/ubuntu jammy-backports InRelease [108 kB]
Hit:4 https://cli.github.com/packages stable InRelease
Hit:5 https://apt.releases.hashicorp.com jammy InRelease
Err:1 http://tr.archive.ubuntu.com/ubuntu jammy InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 871920D1991BC93C
Err:2 http://tr.archive.ubuntu.com/ubuntu jammy-updates InRelease
The following signatures couldn't be verified because the public key is not available:
