SOLVED, here I share my own clumsy appraoch,
starting from a system with secure_mod_insmod = 0
lsmod | cut -d' ' -f1 | sort > insmod0.list
setsebool -P secure_mod_insmod 1
reboot
{ login as root in rescue mode }
lsmod | cut -d' ' -f1 | sort > insmod1.list
diff insmod0.list insmod1.lst --left-column | grep \< | cut -d' ' -f2 > krnlmods
echo "\" "$( cat krnlmods )" \"" > krnlmods
{ this assumes there is an empty /etc/dracut.conf }
echo "add_drivers+=$( cat krnlmods )" >> /etc/dracut.conf
dracut -f initramfs-`uname -r`.img
reboot
This worked well for me and solved the problem of dracut not adding modules from the command-line (which may be due to my inexperience)
Personally I’d expected there to be another way but adding kernel modules to initramfs, I was unable to find an economical approach in short time.