I finally got around to upgrading to 19.07.2 and have found that I am unable to install luci-app-sqm due to a conflict between luci-compat and luci-base.
Model: TP-Link TL-WDR3600 v1
Architecture: Atheros AR9344 rev 2
Firmware Version: OpenWrt 19.07.2 r10947-65030d81f3 / LuCI openwrt-19.07 branch git-20.057.55219-13dd17f
Kernel Version: 4.14.171
root@sigmund:~# opkg update && opkg install luci-app-sqm
Downloading http://downloads.openwrt.org/releases/19.07.2/targets/ar71xx/generic/packages/Packages.gz
Updated list of available packages in /var/opkg-lists/openwrt_core
Downloading http://downloads.openwrt.org/releases/19.07.2/targets/ar71xx/generic/packages/Packages.sig
Signature check passed.
Downloading http://downloads.openwrt.org/releases/19.07.2/targets/ar71xx/generic/kmods/4.14.171-1-342af9e4f67b3447c53216ab8e3b12a1/Packages.gz
Updated list of available packages in /var/opkg-lists/openwrt_kmods
Downloading http://downloads.openwrt.org/releases/19.07.2/targets/ar71xx/generic/kmods/4.14.171-1-342af9e4f67b3447c53216ab8e3b12a1/Packages.sig
Signature check passed.
Downloading http://downloads.openwrt.org/releases/19.07.2/packages/mips_24kc/base/Packages.gz
Updated list of available packages in /var/opkg-lists/openwrt_base
Downloading http://downloads.openwrt.org/releases/19.07.2/packages/mips_24kc/base/Packages.sig
Signature check passed.
Downloading http://downloads.openwrt.org/releases/19.07.2/packages/mips_24kc/luci/Packages.gz
Updated list of available packages in /var/opkg-lists/openwrt_luci
Downloading http://downloads.openwrt.org/releases/19.07.2/packages/mips_24kc/luci/Packages.sig
Signature check passed.
Downloading http://downloads.openwrt.org/releases/19.07.2/packages/mips_24kc/packages/Packages.gz
Updated list of available packages in /var/opkg-lists/openwrt_packages
Downloading http://downloads.openwrt.org/releases/19.07.2/packages/mips_24kc/packages/Packages.sig
Signature check passed.
Downloading http://downloads.openwrt.org/releases/19.07.2/packages/mips_24kc/routing/Packages.gz
Updated list of available packages in /var/opkg-lists/openwrt_routing
Downloading http://downloads.openwrt.org/releases/19.07.2/packages/mips_24kc/routing/Packages.sig
Signature check passed.
Downloading http://downloads.openwrt.org/releases/19.07.2/packages/mips_24kc/telephony/Packages.gz
Updated list of available packages in /var/opkg-lists/openwrt_telephony
Downloading http://downloads.openwrt.org/releases/19.07.2/packages/mips_24kc/telephony/Packages.sig
Signature check passed.
Installing luci-app-sqm (1.4.0-2) to root...
Downloading http://downloads.openwrt.org/releases/19.07.2/packages/mips_24kc/packages/luci-app-sqm_1.4.0-2_all.ipk
Installing luci-compat (git-20.131.47987-bcdb9fd-1) to root...
Downloading http://downloads.openwrt.org/releases/19.07.2/packages/mips_24kc/luci/luci-compat_git-20.131.47987-bcdb9fd-1_all.ipk
Collected errors:
* check_data_file_clashes: Package luci-compat wants to install file /usr/lib/lua/luci/tools/webadmin.lua
But that file is already provided by package * luci-base
* check_data_file_clashes: Package luci-compat wants to install file /www/luci-static/resources/cbi/add.gif
But that file is already provided by package * luci-base
* check_data_file_clashes: Package luci-compat wants to install file /www/luci-static/resources/cbi/apply.gif
But that file is already provided by package * luci-base
* check_data_file_clashes: Package luci-compat wants to install file /www/luci-static/resources/cbi/arrow.gif
But that file is already provided by package * luci-base
* check_data_file_clashes: Package luci-compat wants to install file /www/luci-static/resources/cbi/down.gif
But that file is already provided by package * luci-base
* check_data_file_clashes: Package luci-compat wants to install file /www/luci-static/resources/cbi/download.gif
But that file is already provided by package * luci-base
* check_data_file_clashes: Package luci-compat wants to install file /www/luci-static/resources/cbi/edit.gif
But that file is already provided by package * luci-base
* check_data_file_clashes: Package luci-compat wants to install file /www/luci-static/resources/cbi/fieldadd.gif
But that file is already provided by package * luci-base
* check_data_file_clashes: Package luci-compat wants to install file /www/luci-static/resources/cbi/file.gif
But that file is already provided by package * luci-base
* check_data_file_clashes: Package luci-compat wants to install file /www/luci-static/resources/cbi/find.gif
But that file is already provided by package * luci-base
* check_data_file_clashes: Package luci-compat wants to install file /www/luci-static/resources/cbi/folder.gif
But that file is already provided by package * luci-base
* check_data_file_clashes: Package luci-compat wants to install file /www/luci-static/resources/cbi/help.gif
But that file is already provided by package * luci-base
* check_data_file_clashes: Package luci-compat wants to install file /www/luci-static/resources/cbi/key.gif
But that file is already provided by package * luci-base
* check_data_file_clashes: Package luci-compat wants to install file /www/luci-static/resources/cbi/link.gif
But that file is already provided by package * luci-base
* check_data_file_clashes: Package luci-compat wants to install file /www/luci-static/resources/cbi/reload.gif
But that file is already provided by package * luci-base
* check_data_file_clashes: Package luci-compat wants to install file /www/luci-static/resources/cbi/remove.gif
But that file is already provided by package * luci-base
* check_data_file_clashes: Package luci-compat wants to install file /www/luci-static/resources/cbi/reset.gif
But that file is already provided by package * luci-base
* check_data_file_clashes: Package luci-compat wants to install file /www/luci-static/resources/cbi/save.gif
But that file is already provided by package * luci-base
* check_data_file_clashes: Package luci-compat wants to install file /www/luci-static/resources/cbi/up.gif
But that file is already provided by package * luci-base
* check_data_file_clashes: Package luci-compat wants to install file /www/luci-static/resources/cbi/user.gif
But that file is already provided by package * luci-base
* opkg_install_cmd: Cannot install package luci-app-sqm.
root@sigmund:~#