Is there any possible way to install themes on Nokia 5 without Andromeda app?
Change the wallpaper to a get a darker theme / the usual white theme. It depends on the color of wallpaper in Oreo.Also check Substratum for Android.https://play.google.com/store/apps/details?id=com.lb.lwp_plus
It looks like you're new here. If you want to get involved, click one of these buttons!