jrgd

The Nullobsi fork of Cantata or many other mpd-backed music players are something I can recommend seems to fit what you’re looking for. It supports being able to edit the play queue whilst running a single-track on repeat within it. It does also support fade out and crossfade. The easiest way to obtain it is via its flatpak on Flathub. Cantata can either run an integrated or connect to a system-level mpd server for its backend.