E-scooters

There are good reasons why e-bikes, for instance, are limited to relatively low speeds, and even so their use has resulted in many deaths and serious injuries where take-up has been great, e.g. in the Netherlands or Germany.

Define many? The Dutch reporting I've seen suggests that ebike KSIs have mostly been in the elderly; while the assist has allowed frail users to continue cycling, that same frailty means that falls are more likely to be serious (and IIRC the majority of these KSI don't involve other road users).