Shouldn't it work with that thing on as well?
@Kurt I've done that now. Deleted/disabled all the Samsung and Google (I didn't know about adb uninstall). Installed #trackercontrol to block what I couldn't remove (h/t @mdione). Added F-Droid (Aurora store is also new to me) for VLC, GCompris, OSMAnd. I got APKs for Scratch, Scratch Jr and Audible (with Internet blocked except for when adding books).
Performance seems fine. I'd have liked the purity of LineageOS but this will do.