Why do both my headlights fail intermittently albeit infrequently sometimes, like tonight, in the dark, and then suddenly come back on again of their own accord? The heater fan's on same fuse.

It is is intermittent, the reason will be bad connections. First spray that little brightness adjustment wheel with switch cleaner. That is normally the reason. If that doesn't work, check the plugs up behind the dash.

https://www.google.com/search?q=2019+Subaru+Forester.+The+Dash+lights+go+dark

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Look for the RELAYS for the lights. They are usually on the fuse box. Replace the headlight relay.

Some vehicles use a circuit breaker in the headlight circuit so that when there is a short then the breaker opens and then closes so that night vision is not totally lost from a blown fuse . Check out the system for a blown fuse or faulty breaker or faulty light module.

replace bulbs with factory wattage bulbs. might have aftermarket bulbs and will set a arror code causing this issue

the car probably needs new ignitors or balasts whatever lexus calls them

Nice picture indeed , I would say you have a loose connection.Could be a loose fuse ,Loose relay, Loose wiring , Loose connection the the switch.
The relay could be damaged inside.
I would suggest the Headlight relay as the probable cause.
Usually located in the engine bay in a black box with other relays and fuse's.
If you get someone to flash the headlight as you have described above and listen in the engine bay you should hear a clicking the relay you are looking for should be near that .
Hope this helps and let me know if you need more help.

Sounds like you switch is overheating. Yiu should be able to get it home.

It sounds like you have a loose ground wire somewhere. If you can't find it, tonight, when it's dark, have somebody turn all this stuff that's giving you problems, on and off, while you watch for sparks.

my advise to you is to take the car to a brake specialist as your brakes are the most important part of the car where no expence should be spared you may even save a life your own i am vert serious not being rude i assure you good luck Linds

Could be corrosion or a broken prong socket.