Flashing an image that doesn't pass signature verfication seems not like a good idea. Please verify your image before flashing it.
Which instructions did you follow? The one from LineageOS has a section "Installing LineageOS from recovery". Please read the full instruction before doing anything. Have you followed the mentioned steps there already?
jtx board - Journals, notes, tasks
OpenTracks - Sports tracker
Öffi - Public transport navigator
ViMusic - Listen to music from YouTube