I have the same problem on Orange Pi PC

rmbianmonitor -m
12:15:42:   ---      0.06  15%   4%   9%   1%   0%   0%/usr/bin/armbianmonitor: line 388: read: read error: 0: Invalid argument
/usr/bin/armbianmonitor: line 389: [: -ge: unary operator expected

cat /etc/armbian-release
# PLEASE DO NOT EDIT THIS FILE
BOARD=orangepipc
BOARD_NAME="Orange Pi PC"
BOARDFAMILY=sun8i
BUILD_REPOSITORY_URL=https://github.com/armbian/build
BUILD_REPOSITORY_COMMIT=fef01045-dirty
DISTRIBUTION_CODENAME=bionic
DISTRIBUTION_STATUS=supported
VERSION=20.11.6
LINUXFAMILY=sunxi
BRANCH=dev
ARCH=arm
IMAGE_TYPE=stable
BOARD_TYPE=conf
INITRD_ARCH=arm
KERNEL_IMGE_TYPE=Image

 

Providing logs with 

armbianmonitor -u

 helps with troubleshooting and significantly raises chances that issue gets addressed.

pi@RetrOrangePi:~$ armbianmonitor -u

Network/firewall problem detected. Not able to upload debug info.
Please fix this or use "-U" instead and upload whole output manually

 

3 hours ago, Илья Козлов said:

Please fix this or use "-U" instead and upload whole output manually

So armbianmonitor -U

Using sudo is also a good idea if some resources used by armbianmonitor needs root privileges.

If I remember well it solves this issue last time I tried.

 sudo armbianmonitor -U | pastebinit
/usr/bin/armbianmonitor: line 388: read: read error: 0: Invalid argument
/usr/bin/armbianmonitor: line 389: [: -ge: unary operator expected
/usr/bin/armbianmonitor: line 388: read: read error: 0: Invalid argument
/usr/bin/armbianmonitor: line 389: [: -ge: unary operator expected
/usr/bin/armbianmonitor: line 388: read: read error: 0: Invalid argument
/usr/bin/armbianmonitor: line 389: [: -ge: unary operator expected
/usr/bin/armbianmonitor: line 388: read: read error: 0: Invalid argument
/usr/bin/armbianmonitor: line 389: [: -ge: unary operator expected
/usr/bin/armbianmonitor: line 388: read: read error: 0: Invalid argument
/usr/bin/armbianmonitor: line 389: [: -ge: unary operator expected
/usr/bin/armbianmonitor: line 388: read: read error: 0: Invalid argument
/usr/bin/armbianmonitor: line 389: [: -ge: unary operator expected
/usr/bin/armbianmonitor: line 388: read: read error: 0: Invalid argument
/usr/bin/armbianmonitor: line 389: [: -ge: unary operator expected
/usr/bin/armbianmonitor: line 388: read: read error: 0: Invalid argument
/usr/bin/armbianmonitor: line 389: [: -ge: unary operator expected
/usr/bin/armbianmonitor: line 388: read: read error: 0: Invalid argument
/usr/bin/armbianmonitor: line 389: [: -ge: unary operator expected
/usr/bin/armbianmonitor: line 388: read: read error: 0: Invalid argument
/usr/bin/armbianmonitor: line 389: [: -ge: unary operator expected
http://paste.ubuntu.com/p/42StCf2NhS/

 

20138	hi  linux-dtb-dev-sunxi                   5.97                                 armhf        Linux DTB, version 5.2.14-sunxi

Try using

a) an actual supported branch and

b) up-to-date packages

apt-get install linux-dtb-dev-sunxi

dpkg -l |  grep linux-dtb-dev-sunxi
ii  linux-dtb-dev-sunxi                   20.11.7                              armhf        Linux DTB, version 5.10.4-sunx

solved the problem

Thanks