One approach I started using a could of years ago was storing SSH private keys in the TPM, and using it via PKCS11 in SSH agent.
One benefit of Microsoft requiring them for Windows 11 support is that nearly every recent computer has a TPM, either hardware or emulated by the CPU firmware.
It guarantees that the private key can never be exfiltrated or copied. But it doesn't stop malicious software on your machine from doing bad things from your machine.
So I'm not certain how much protection it really offers on this scenario.
Linux example: https://wiki.gentoo.org/wiki/Trusted_Platform_Module/SSH
macOS example (I haven't tested personally): https://gist.github.com/arianvp/5f59f1783e3eaf1a2d4cd8e952bb...