You have more problems than a neutral light / switch then.
Bypass the sidestand switch to eliminate that possibility. Not just unplug it, you have to jump 2 wires on the harness side connector. Just did my 92, but can't remember what 2 wires off the top of my head. Refer to the wire diagram. Does your sidestand switch light function on the dash at this time?
Bypass the clutch switch on the clutch master cylinder to eliminate that, but be sure the bike rolls in neutral before any subsequent start attempts.
Sounds like the clutch diode on the wire harness has failed and is possibly what you are referring to in your first post you read about. Can't remember exactly where I noticed it was located on my 92 recently, but it is not located under the carbs, I know that. Likely on the right side near the coil, to perhaps the rear tank mount area.
It is possible that every function got fried somehow, but is unlikely. I'm pretty sure there's a combo that will still allow the bike to start even with a bad diode. Bike doesn't think sidestand is down and believes the clutch lever is pulled in.
There are people here way better at walking thru diagnosing electrical problems than me. Well, at least better at explaining it and the logic. But eliminate the suspects until it starts and then start re-introducing them until it doesn't. Guess that's all I got right now.