Synopsis: I think you've just re-complicated something that took a while in this thread to simplify.
And buying a new TV is not considered an option, the roughly $100 solution being proposed is expensive enough.

On Thu, Nov 30, 2023 at 11:19 AM D. Hugh Redelmeier via talk <talk@gtalug.org> wrote:
 
General concern: the complex chain of devices has many points of failure.  Getting it to work might be difficult.  Keeping it working might be difficult.

The consensus as I read it so far was:

1. Off-the-air antenna
2. ATSC digital tuner
3. Karen's existing TV
4. Coaxial cable from tuner to TV

That's all.

The antenna has no moving parts and does not even need external power if its optional amplifier is not required.
The ATSC tuner has one cable in, one cable out, and power.
Operation will be no more complex than the Bell box that Karen is trying to replace (but not much less complex either).
 
General concern: many components these days expect navigation of on-screen menus.

Yes, but so do the original TV and the Bell Fibe box. That is a challenge that can't be bypassed in order to achieve what is being asked for.

General concern: some HDMI signals (eg. from Rogers or Bell) are "protected" by HDCP.

I have no idea how this got injected into the topic at hand. Using an antenna to receive off-the-air broadcasting completely bypasses Rogers and Bell.
As Karen's TV does not have an HDMI-in this is a complete non-issue.
The connection from the ATSC box from Karen's TV can be done either by coaxial cable (and both devices will need to agree on Channel 3 or 4 using physical switches) or by an RCA-to-RCA video cable.

As for copy protection ... under this scheme there is none. The ATSC video adapter even has a PVR function that enables one to set a timer and it will store any channel's feed to a user-supplied USB drive. Unfortunately, the setup and operation of this is all done using the remote control and on-screen prompts.

- Evan