https://www.sciencealert.com/zooming-black-holes-can-reach-10-the-speed-of-light-scientists-say
https://www.sciencealert.com/zooming-black-holes-can-reach-10-the-speed-of-light-scientists-say
Probably relative to the CMB (the frame of reference where there is no redshift or blueshift bias in any direction).
But what if all nearby objects are moving towards it at a similar speed? Or away? At such a large scale speed becomes a mind bending thing.
No other large object will be moving close to that speed so it'll be almost like they are standing still.