Pretty much, nothing.
If you have a DIRECTV DVR and it breaks, you should recycle it or return it to DIRECTV if they want it back. If you leave DIRECTV, you should return their equipment to them or recycle it.
DIRECTV DVRs can’t be used for over-the-air reception. They can’t be used for other services. If you don’t have to return them, you can strip the hard drives out but remember that they’ve been sitting in your dusty entertainment center for years. Those drives could fail at any time.
You can’t pull recordings off a DIRECTV DVR unless you use a video capture system which takes one hour for every hour you want to transfer. You can’t give them to friends even if DIRECTV doesn’t want them back.
Bottom line, it’s a sad but true fact that once a DIRECTV DVR has served its purpose for you, there isn’t a lot you can do with it, period.