OK. So kde uses some automounting tool, doesn't it. I haven't used kde in years. I see it as bloatware.
but get to that tool, and try to configure that. Also, lines in /etc/fstab are cheap. Why not add linnes for sdb1, sdb2, sdb3, sdb4, sdc1, sdc2 etc with a 'ro' option. Then all are mounted read only