ORBI - LG TV (wifi 5ghz) only connects to 2G.

Is your TV connected to the router or satellite?  It most likely is connecting to the router, as it is the first WiFi that the TV sees any time that the router reboots.

If so, then you have encountered one of the Orbi's design flaws.  The routers WiFi is enabled long before the satellites WiFi for clients to bind to.  Smart TVs are not expected to roam, so they will bind to the first WiFi signal they see, and will not look for a stronger signal unless they are rebooted.  So your only way to get them to bind to your closer satellite instead of the router is to reboot (power cycle) the TV.

I likewise have this issue with an IP camera and smart garage door opener at my home.  My workaround for them was to add a smart plug on the power for each.  I have a UPS on my router so it should not loose power unless I have a long power outage, so I typically will know when I have rebooted my router.  So when I do reboot it, I will then power-cycle the smart plugs for my garage systems so that they bind to the closer satellite instead of the weaker signal from the router.

A possible workaround is to reduce the power of the 2.4GHz signal so that they TV binds to the 5GHz signal instead.  Try 50% or 25% power levels to see if that helps without affecting other devices.  This workaround did not work for me, as I had to reduce to 25% before my garage would bind to the closer satellite, but then other 2.4GHz devices throughout the house had poor signal as well.

NG could probably correct this issue in their firmware, I submitted a ticket to them for the issue and they said they do not plan to fix it.  I do not know if other vendors mesh systems suffer from this same issue.