As far as I understand, without any work (energy consumption) that is directly tied to the value of the asset, there's no argument left for it to be a currency, i.e. it can only be categorised as a security asset.
Buying Eth: No investment in a common enterprise, no expectation of profit nor is that non-profit derived from others. Not a security.
Staking Eth: Investment in common enterprise, expectation of profit and profit derived from others. Looks and quacks like a security.
Buying and holding Eth without staking it shouldn't be considered a security, while staking said Eth should be considered a security. At least if we're still following the "Howey Test".
If there were two tokens, one of which was stakeable and the other not, traded separately but convertible, then sure. But that's not reality. ETH's value is in part defined by its ability to bear interest. Whether you personally stake or not has no bearing on whether your ETH is a security.
Staked ETH derives profit from your own effort. You have to buy equipment (consumer-grade computer), pay for internet and energy costs to have it plugged and put your own effort in maintaining it online, operational and secure. This is basically a side-job for techies but a side-job in the end. Staked ETH rewards are thus not passive income and staked ETH is not a security. In a similar manner that rental income is taxed as income and a landowner that rents an appartment is not issuing an illegal security.
A different thing is what happens with a liquid staking token like stETH, a much better argument can be made that it quacks and walks like a security.
The profit is to be derived from the efforts of others. People staking at this point are entirely dependent on the Foundation to add the ability to withdraw your staked ETH. Do stakers expect to make a profit if the Foundation doesn't add this feature?
The foundation doesn't add anything because they don't write the clients. The foundation does research and gives grants using its resources to fund specific areas and fund related infrastructure. The next upgrade and what it includes is agreed by the various open source clients and is enforced by the validators when they decide to upgrade and implement the changes.
Besides that important clarification, validators are already receiving income for their efforts. The tips and MEV are already flowing to their wallets as we speak, it's only the issuance that is locked. The particular change required to unlock funds is rather trivial and can be implemented on your own even if you wanted to. But doing so without a large consensus of validators would fork you out of the main chain and those unlocked coins could be rather useless, this should show the delicate balance that decentralized consensus involves.
Staking Eth: Investment in common enterprise, expectation of profit and profit derived from others. Looks and quacks like a security.
Buying and holding Eth without staking it shouldn't be considered a security, while staking said Eth should be considered a security. At least if we're still following the "Howey Test".