If it seems like hot reloading or anything that depends on file-watching isn't working on Linux, you're probably running into inotify limits. As a quick check, try doing

tail -f (some file)

If you get

tail: inotify cannot be used, reverting to polling: Too many open files

then that's a telltale sign of running out of inotify watches. For more details, do (in bash)

echo "pid    watches cmd"; for x in $(find /proc/*/fd/* -type l -lname 'anon_inode:inotify' 2>/dev/null); do PID=$(echo $x | cut -f 3 -d'/'); FD=$(echo $x | cut -f 5 -d'/'); WATCHCOUNT=$(grep -c inotify /proc/$PID/fdinfo/$FD); CMD=$(cat /proc/$PID/cmdline | sed 's/\x0/ /g'); echo "$PID       $WATCHCOUNT     $CMD"; done | sort -k 2 -n -r

which prints a list of commands with inotify watches sorted by number of watches in decreasing order. On my system, flow and storybook use up about 11000 watches. (See this StackExchange answer for an explanation for the above one-liner; however, its command is slower due to using lsof.)

See this link for how to increase the watch limit; I set mine to 65536.