There has been a change in how to select bones in Blender 4.0. To select a bone, hold Shift + Ctrl + LMB. Like sculpting mode, holding Ctrl removes weight. Holding Shift smoothes out the weight.
Grant has a video about this.
Weight Painting Updates in Blender 4 - YouTube
Hi admin, any chance to pin this post to the Blender Character Creator v2.0 course, in section Animating A Snake?