What do I do with this wireless router?

I got this T-Mobile CellSpot router (Asus RT-AC68U variant, TM-AC1900) a long time ago as part of some promo/deal and bought a few. This one's bricked now (won't boot, tried recovery mode).

Called T-Mobile support a few months ago —they have zero records of it linked to my account (still active customer). Said nothing's tied to me, no issues.

Want to flash it to stock Asus firmware or just dispose if unrecoverable. Question: If I wipe/adjust it off and keep using/toss it, will they ever come back years later with a non-return fee or billing surprise? Anyone have experience keeping these old CellSpots with no records? Did T-Mobile ever chase you down?