More stuck up inside the spring perch - be it upper or lower
Might also be a worn lower bush.

Try specifically spraying wd40/lithium grease in just the lower bush area - see if that stops the squeak. Try on the lower perch and ditto. You should be able to find the area quickly.

Finally take out the coilover/s , disassemble and clean. Make sure to test the shock piston on each coilover for consistent travel and no leaks !