Anyone who is concerned about this should already be using full-disk encryption, which means the memory contents are actually better protected during hibernation than in a live state.
This is one thing that usually Linux gets mostly right .. only if the proprietary GPU drivers played along. Meanwhile, Microsoft and Apple certainly could implement this properly but instead decide to release a new half-assed half-hibernation after another.
AFAIK this is only an issue if you think UEFI Secure Boot and TPM are a good idea. The traditional way to implement full-disk encryption on Linux is by disabling UEFI validation and deriving the key from a passphrase rather than storing it in the TPM.
Personally I'd rather keep secure boot and just disable the kernel lockdown feature. You still gain a significant amount of security while maintaining functionality that way.
