This fix applies to issues when your HDMI connection between MacOS and TV has never worked. If your HDMI used to work but stopped, then you simply undo whatever you did that may have caused it.

You can detect the issue when your TV or external monitor connects for a second or so, then disconnects, and after a few seconds tries to connect again. When that happens, your computer screen settings might flash shortly on TV. You can safely ignore all the HDMI-MacOS "solutions" offered by dozens of websites including Apple and TV manufacturers as they are NOT WORKING:

• Fiddling with display settings like variable refresh rate etc.
• PRAM reset
• Cleaning HDMI connections
• Trying different HDMI ports
• Trying different Thunderbolt ports
• Updating your OS (this bring you often more problems than it solves)
• Enabling or disabling HDMI-CEC from TV settings
• Updating your TV firmware (seriously, I would never let a TV connect to Internet, phone home and open up to hackers)
• Installing some shady app which is offered as a solution. This will probably get your computer compromised and let hackers in. Never install anything that is offered for solution to whatever problem you might experience.
• Apple is simply asking to contact the TV vendor when this happens. Trying to contact TV vendor is complete waste of time. None of the TV operating system vendors have proper bug tracking systems or developer communities and all you get, if you are lucky enough to get any answer, is to turn your computer off and on again.

All of these "solution" create you more issues, waste your time and in the worst case they will mess up your Mac so badly that your only option is to re-install the operating system. If you want to try them, make a full backup and create an operating system recovery media first to be able to rollback later.

How to fix the issue?

The solution to the issue is very simple. There is a compatibility issue between Mac Thunderbolt and TV. The solution is to find a way to make the connection so that both TV and MacOS work. The easier is to have an USB-C to HDMI cable that matches the speed requirements of your TV (8K, 4K or standard). Here are the speed requirements for Mac hardware. A bit more complicated solution is to find a USB-C dock or adapter for the HDMI connection in which case you have 2 moving parts that might cause the issue: adapter/dock and the cable. If either of them is not compatible, the connection will not work. I got it working after wrestling 8 months with Apple (total waste of time), the TV manufacturer (total waste of time) and TV seller, who kept blaming everyone. Both keep blaming each other and they are not interested in the customer or finding a working solution. I took the computer, my dock, and HDMI cable to the shop the sold the TV and sat there until we found a cable that worked. Both my dock and old HDMI cable were not compatible causing the issue.

If this solution does not work, then the issue is really with the MacOS and your TV, and you are fucked.

Apple is to blame for the issue

The issue causing the problem is the lack of a proper error message in MacOS (at least in Apple Silicon, M2 or higher, Ventura or newer). The OS should inform the user that the HDMI connection was lost due to an error and the OS will keep trying to reconnect after a few seconds. Instead, the TV keeps appearing and disappearing from Screen settings while TV/external monitor is blinking. And the lack of debugging tools and public technical documentation including the OS source code makes fixing the bug not doable. Because there is no proper error message, the user has no idea what is happening. Don't bother reporting this to Apple as those zealots will dismiss MacOS error reports and improvement proposals as smearing attempts. Apparently their perfect system does not have any bugs and can not be improved. As Apple is a cult and users mainly clueless, they can be easily fooled to compromise their computers with malware and malicious solutions.

Happy hacking,

Santeri