How can I change lockscreen in macOS Big Sur?

I hate the lockscreen image in macOS Big Sur and would like to change it. I have read, and tried, everything I could find here and online, but nothing works. I am using a Dynamic Wallpaper, so none of the images from there are used as the lockscreen, just that mishmash of horrid colors.

My questions are: Can the lockscreen image be changed? And, if it can, how can it be done?

Thanks!