I had the blank screen problem after changing from v18 to v19 too.
I found I had to enable hdmi_ignore_cec in the myOSMC settings so I now have
the following line in /boot/config-user.txt
hdmi_ignore_cec=1
Note that it’s “hdmi_ignore_cec” not “hdmi_ignore_cec_init” as you had in your original post.
Regards
Jim J