I own two Glove80s, but for me the ultimate split keyboard with a thumb cluster was the Dygma Defy, of which I now own a pair as well. Couldn't recommend it enough. https://dygma.com/pages/defy

The designers were extra mindful of different thumb lengths, making it so that you can usually find a configuration that feels natural and not cramp up your joints: https://dygma.com/blogs/product-development/how-we-developed...