Linear issues: https://linear.app/comm/issue/ENG-2547/restyle-sidebarlistmodal-and-subchannelslistmodal, https://linear.app/comm/issue/DES-20/designs-for-subchannels-modal
SidebarListModal, SubchannelsModal use ThreadListModal undeneath, and no other component uses ThreadListModal. SidebarListModal and SubchannelsModal are supposed to look consistent, and match the new designs provided in the second linked
issue.