How about a dongle that plugs in to an HDMI port on TV or monitor that would allow view only access of all cams at once?
Please see, vote for and/or comment on the following existing #wishlist topics:
These are easily found by searching #wishlist for “TV” using these links:
I’ll add to this list.
You can use a mobile to HDMI adapter. I’ve seen USB-C, micro-USB and lightning connectors. I use one myself.
They are available on Amazon.