The year it happened to me, got super lucky that a group in the next room over -- with the same system -- had a friend who had to not go to GenCon for lost job reasons like the week before. And they were selling her tickets to events as they went. Since my event was cancelled and refunded, as I found out 30 minutes prior, I bought their spare ticket and had fun. And my event was cancelled due to a positive covid test right before cancellation.

If incentivised correctly, I'm confident that Gen Con could get a pool of backup DMs who would not otherwise have run games. At my D&D club, there are 'Emergency DMs' who are able to run a game if one of the main DMs drops out; they have a marginal preference for being players but are happy to DM when the need arises. The system works very well. In the 18 years since the club started, no-one has ever been turned away because there wasn't a game for them.  

I submitted my wish-list within seconds of the Events registration going live but was still only 12,000th-and-something in the queue, so didn't get into a couple of 5e D&D games that I was very interested in. The only 5e games available at roughly the same times were being run by a particular DM/club. There were some irregularities in the listings of their games that make me concerned. I prefer not to say what those irregularities are because if I do, it would identify the DM/club and I don't want to cast unfair aspersions. 

I was not aware that you could sign up for 5e D&D games with particular companies? Is there a parallel or shadow registration process outside of the Gen Con Events registration? If so, where?

Thank you for the tip about monitoring other games for available slots. Is that something you do online or by milling around where lots of other games are being run?    

What is the games library? Where is it? And how does it work? 

I think there are limits to what Gencon can do.   Who wants to go to Gencon to volunteer to be a backup and potentially do nothing for blocks of hours 'just in case' and potentially never use whatever they designed or worked on.    I'd rather just find something else to do in a case like that rather than just have a GM inserted that might not even be remotely prepared.

The games library is board game centric not RPG related.

They are all in the system. You can find the organization running the game under the gaming group information. "Baldman Games" runs plenty of 5th Edition games. Just search for "Baldman"

You can always search for games online. to find a new one.

Search "Games Library" for tickets to it. It is boardgame centric and you check them out or join a group. If sold out you can usually get in with Generic Tickets.

There is also FEPH First Exposure PLaytest Hall. https://www.gencon.com/gen-con-indy/first-exposure-playtest-hall-feph

Open Gaming is also available in the Marriott.

And you will probably find that you have not put enough time aside for the Exhibit Hall....

Mike

If you volunteered to be a backup DM, you wouldn't risk 'do[ing] nothing for blocks of hours'. You would volunteer for a particular slot, say 10am, and each substitute game would be fixed at, say, 3 hours. If you were required, you would be notified within the first 30 minutes, i.e. by 10.30am in my example. If you weren't required, you would be free to do whatever you liked after 10.30am in my example. You would be incentivised either way though the incentive if you were required would be greater. If you're thinking that not being required would itself leave DMs gameless, bear in mind that a) they would still get some incentive and b) they would know what the probability of not being required would be as Gen Con could estimate it from historical data; they could plan for that contingency or, if there were sufficient unused backup DMs, they could form a game themselves.
As for the idea that backup DMs would be unprepared, I don't accept that based on experience. They could bring something they had run before in their home games or at other conventions.

Regarding the Games Library, while I don't dislike boardgames, I'm not a big fan of them either. Knowing that there is a Games Library is no doubt useful for some reading this thread, but it's not a solution for everyone. 

    

What I am getting from this is that you want to play as much RPG, specifically 5th edition D&D, as possible.  It looks like there are still hundreds of 5th edition D&D games with open slots.  If a Thursday 8AM game in the stadium was cancelled, at the moment there are 3 others in the stadium with open slots.  That's the kind of thing I was talking about, but checking day of/right before you would potentially need the slot so you would have a close by backup.

Also, consider overbooking yourself to the point where you will end up being happy if one gets cancelled, because you wanted a chance to go to the dealer hall/eat/etc.  [This is not what I would normally recommend, but you seem to be really focused].

Do you DM at all?  It seems like perhaps working up a D&D 5th edition one shot and heading over to open gaming at the Marriott might also be a decent backup for you.

 

I have to be honest, I have a hard time visualizing who GenCon would recruit to act as a volunteer "backup DM". You'd need someone who is A) ready, willing and able to go all the way to GenCon and run a game for a group of strangers, but is also B) willing to sit in a bullpen to possibly play their game with a group of people who literally would rather be doing something else instead of getting a proper slot with a proper player group who have actual buy-in. 

If they're in it for the pleasure of the game, why wouldn't they just run it on their own?

If they're trying to rack up event host hours for compensation purposes, why wouldn't they take the more sure deal of scheduling their own block versus risking reduced compensation if they block out their time and don't get called up?

If they're hoping to get a bunch of "easy money" (in whatever form the Con would reward backup duty) by volunteering to cover a slot while actually hoping they don't get called, do you even want to be stuck in that person's game?

I have allowed 6 to 8 hours to the Exhibit/Trade Hall. I’m hoping that’s enough as my shopping list is fairly narrow and my capacity to bring gaming goodies back is limited by airline luggage allowances.

Your suggestion of running a game myself in the event of a DM no-show is an excellent one except for the facts that I like using lots of paraphernalia (DM screen, battle mat, miniatures etc) but am limited in how much I can bring by airline luggage allowances. I may resort to what I did in my university days and resort to ersatz substitutes (coins & dice instead of miniatures etc). 

It would have to be suitably incentivised. I’m not familiar enough with the incentive scheme for the DMs who are already committed to be able to suggest exactly how the standby DMing should be rewarded, but strongly suspect from years of backup DM provisioning that it can be made to work.