Soul speed boots can't be taken off, just like curse of binding would be.

Diamond boots with umbreaking, protection, mending depth strider and feather falling from older version got enchanted with sould speed enchantment in 1.17. Now, every time it passes through a soul sand it can't be removed. Only way to remove found was right clicking another boots in the hotbar, wich exchanges the boots. The second boots can be removed.
Cleary non of the boots have the actual curse of binding.