I listen to podcasts to get to sleep. I have some earbuds that I can use single-sided, and either of the sides can connect on their own (doesn't have a master/slave connection where only one actually connects to phone and slave connects to master)

I go to bed with one or the other. During the night I might switch the bud to the other side, both sides can fit in either ear falling out and the sound is fine, even though they're designed for only one ear. YMMV with that.

But this is the best way I've found.

There's little Bluetooth speakers or vibrator bars that are designed to sit underneath your pillow and they're quiet enough that a partner won't hear it, but you can. I've tried those as well but you have to have your head on the pillow in a specific way for them to work and I don't like being "confined" to that specific position.

I lay on my back and both sides so this works best for me.