Update to my last post: the Timberland Boot Kit helped a bit, with a few cycles of brushing and cleaner and then conditioner. But what ultimately helped most was dried bread. :
How to Clean Timberland Boots (Renewbuck Review) - YouTube
Shop Timberland Product Care Boot Kit TB0A2JWV000 beige | SNIPES USA
Timberland TBL® Nubuck Leather Boot Kit at Von Maur
Boutique Tapage - Timberland Balm Proofer . Timberland Renewbuck . Timberland Boot Sauce . Timberland Dry Cleaning Kit . Timberland Rubber Sole Brush . All what you need for your Timberland Boots
How to Clean My Timberland Boots | Timberland - YouTube