These types of programs have gone through a few iterations since the secure enclave was released, but they all share a fatal flaw, probably from the SE itself:
You can only store keys that use the NIST P curves, which are not recommended for SSH, or any serious crypto. There are serious supicions that they were tampered with during design by NSA, and are listed in djb's https://safecurves.cr.yp.to/ as unsafe. Using this program would force you to configure your server to accept keys using unsafe curves.
Better than having then unencrypted (unless you set a passphrase) on the filesystem for every rogue process to grab. The issue with password managers is the key is then most likely still accessible from other processes while the password manager is unlocked. On linux for example by poking around in /dev/mem or /dev/kmem. There are way that help with that like memfd_secret. A secure enclave or similar side processor avoids this issue by running within its own isolated memory and this processor also handles all key operations, so the key never enters the main memory.
The readme specifically mentions Yubikey support. Given the restrictions with Secure Enclave (no import, export, or backup), a smart card or Yubikey probably would be better.
I can recommend this guide [1] to setup your yubikey with gpg, which allows you to both use it to sign or encrypt with gpg and also to use it as an ssh key.
Looks like this is only for Macs with Secure Enclaves. Does Apple's own Keychain app not do this? I would have thought that would utilize Secure Enclave too.
You can only store keys that use the NIST P curves, which are not recommended for SSH, or any serious crypto. There are serious supicions that they were tampered with during design by NSA, and are listed in djb's https://safecurves.cr.yp.to/ as unsafe. Using this program would force you to configure your server to accept keys using unsafe curves.