These files can be flashed from TWRP.
Most of these have only been tested on Lineage OS 14.1 and Lineage 15.1.
keys-official-to-xdn.zip (~11 KB) - Flash this from TWRP to switch your Lineage OS keys from Official to XdN. This is needed before flashing an XdN build of Lineage OS over an Official build.
keys-xdn-to-official.zip (~11 KB) - Flash this from TWRP to switch your Lineage OS keys from XdN back to Official. This is needed before flashing an Official build of Lineage OS over an XdN build.
fs-trim.zip (~2 KB) - Flash this from TWRP to run TRIM on /data, /cache, and /system.
font-ubuntu.zip (~145 KB) - This replaces the stock Roboto font with the Ubuntu font.
Old versions of Open GApps:
open_gapps-arm-7.1-pico-20180910.zip (~105 MB)
open_gapps-arm-8.1-pico-20180910.zip (~104 MB)
open_gapps-arm64-8.1-pico-20180910.zip (~110 MB)