NX Jetpack install report error in custom board

Hi,We make the OS image with version Jetpack4.6 adapt in our custom board

then login the system we try to install and update the additional package by apt

but console print the error

E: Unable to locate package nvidia-jetpack

So we search topic like this and try to modify the source list,also report error

ubt@ubuntu:/etc/apt/sources.list.d$ sudo apt update
Hit:1 Index of /ubuntu-ports bionic InRelease
Hit:2 Index of /ubuntu-ports bionic-updates InRelease
Hit:4 Index of /ubuntu-ports bionic-backports InRelease
Get:3 https://repo.download.nvidia.cn/jetson/common r32.7 InRelease [2,555 B]
Get:5 https://repo.download.nvidia.cn/jetson/t186 r32.7 InRelease [2,549 B]
Hit:6 Index of /ubuntu-ports bionic-security InRelease
Err:3 https://repo.download.nvidia.cn/jetson/common r32.7 InRelease
The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY 0D296FFB880FB004
Err:5 https://repo.download.nvidia.cn/jetson/t186 r32.7 InRelease
The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY 0D296FFB880FB004
Reading package lists… Done
W: GPG error: https://repo.download.nvidia.cn/jetson/common r32.7 InRelease: The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY 0D296FFB880FB004
E: The repository ‘https://repo.download.nvidia.com/jetson/common r32.7 InRelease’ is not signed.
N: Updating from such a repository can’t be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: GPG error: https://repo.download.nvidia.cn/jetson/t186 r32.7 InRelease: The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY 0D296FFB880FB004
E: The repository ‘https://repo.download.nvidia.com/jetson/t186 r32.7 InRelease’ is not signed.
N: Updating from such a repository can’t be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

Now we want to know how to fix the error and avoid face this question during we make the install image

Thank you

Issue similar as Jetpack 4.5 Unable to locate package nvidia-jetpack - Jetson & Embedded Systems / Jetson TX2 - NVIDIA Developer Forums

Hi,This issue not solve I mentioned question. Thanks