Believe it or not, I value businesses and occasionally do some valuation work related to marital dissolutions. I have valued timeshare companies and receivables and timeshare interests in the past. (I have been valuing businesses and business assets for over 25 years now.). In the 1990s, these interests did have some resale value (not a lot in most cases, usually 10% to 20% of original cost for fixed or flex weeks but more if points in a points system). Unfortunately, the market has cratered in the past 20 years, especially since 2007. You can go on Ebay and see timeshares sold (and not sold) for $1.00, $100, or $1000 asking prices. The same on TUG. Listings for sale are usually not much more than wishing in reality and are not reliable.
It is sometimes hard to believe that something people pay $15K, $20K or even $30K for in a sales presentations by a significant company might be worth only cents on the dollar when resold, but that is the reality of an inefficient and illiquid market where too many people currently want to get rid of their timeshares just to avoid the hassle (including credit rating damage for non-payment) and cost of the annual maintenance fees (plus the exchange and other fees if they want to actually use the timeshare but exchange for different dates at the same or other resorts). Unless the timeshare is in a prime or highly desirable location (and/or particularly desirable time of the year) with a more limited supply of timeshares available for use or exchange (high points value for exchanges on RCI or II) and has more reasonable annual maintenance fees, it will typically be hard to sell for any significant amount currently. There are just too many affordable alternative rental options now in the market to make the upfront costs and commitment to annual maintenance fees worthwhile for many people.
If you list the timeshare on Ebay and then the other listing sites (which list for a nominal fee or only charge you based on successful sale) and cannot find a buyer, then it may even make sense to "quit claim" the unit if they will allow it after the debt is paid off. You might investigate entities that will do the closing services for you and the buyer (often the buyer will pay to close and assume the maintenance fees).