jless captures all mouse events, preventing terminal-native text selection and copy. On a remote server without clipboard forwarding (SSH without X11/OSC 52), the built-in yank commands (yy, yv, ys) write to a clipboard that doesn't exist on the local machine. There is no flag to disable mouse capture.
jless has no --no-mouse flag. Workarounds: (1) Hold Shift while dragging to bypass TUI mouse capture in most terminals. (2) Use pp/pv/ps print commands instead of yy/yv/ys — these print to stdout with mouse tracking temporarily disabled. (3) For bulk work, use jq instead: jq -C '.' file.jsonl | less -R.