homebrew – After installing openssh 8.2 via brew, how do I add keys to keychain?

I installed openssh 8.2 via brew install openssh. I added the following to my .profile:

export SSH_AUTH_SOCK=”~/.ssh/agent.$HOST.sock”
ssh-add -l 2>/dev/null >/dev/null
if ( $? -ge 2 ); then
ssh-agent -a “$SSH_AUTH_SOCK” >/dev/null
And then I have to do the following:

ssh-add ~/.ssh/id_ecdsa_sk
Enter passphrase for /Users/myuser/.ssh/id_ecdsa_sk:
Identity added: /Users/myuser/.ssh/id_ecdsa_sk
even though I have the following in my ~/.ssh/config:

Host *
IgnoreUnknown UseKeychain
UseKeychain yes
AddKeysToAgent yes
IdentityFile ~/.ssh/id_ecdsa_sk

(I had to add the IgnoreUnknown bit because the install from brew installs a version that breaks the UseKeychain bit.) But now: how do I wire it up so it adds the key to my keychain?