I just made an upgrade from 19.07.5 to 19.07.6. Then I re-installed adblock together with the correspondent lucy file. However,
opkg_download: Failed to download http://downloads.openwrt.org/releases/19.07.6/packages/arm_cortex-a7_neon-vfpv4/luci/luci-compat_git-21.041.07141-8674e2a-1_all.ipk, wget returned 8
Checked the download page. The listed packages for luci in arm_cortex-a7_neon-vfpv4 are significantly less than for other systems, and of course the 'luci-compat_git' file is missing.
It turned out that no luci packages has been upgraded by the upgrade process, nor can any of them be manually upgraded, irrespective of through luci or terminal.
Not sure whether downgrading will solve the issue, as packages for all 19.07.X releases point to this directory.
So what to do?