Hi,
The build error is not related to INFO: Failed to copy built images to tftp dir: /tftpboot
This is the error
tar: This does not look like a tar archive
tar: Skipping to next header
tar: Exiting with failure status due to previous errors
It would appear that you are using the incorrect pre-built image (/home/solone/Downloads/delete/PYNQ/sdbuild/bionic.aarch64.2.6.0_2020_10_19.img)
Since 2.7, merged in master, the prebuilt and intermediate images are tarballs. Please download the correct prebuilt image for 2.7 from here
PYNQ rootfs aarch64 v2.7
Mario