pfSense

In the OpenVPN client config, in order to use tls-crypt-v2,

I uncheck "Leave TLS Key":
Cryptographic Settings -> TLS Configuration -> [ ] Use a TLS Key

Under Advanced Configuration -> Custom options, I insert the tls-crypt-v2 tag at the end of the custom config section, like so:

#only repeat logged warnings 3x:
mute 3

<tls-crypt-v2>
-----BEGIN OpenVPN tls-crypt-v2 client key-----
KEY_GOES_HERE_KEY_GOES_HERE_KEY_GOES_HERE_KEY_GOES_HERE
KEY_GOES_HERE_KEY_GOES_HERE_KEY_GOES_HERE_KEY_GOES_HERE
KEY_GOES_HERE_KEY_GOES_HERE_KEY_GOES_HERE_KEY_GOES_HERE
-----END OpenVPN tls-crypt-v2 client key-----
</tls-crypt-v2>

3) Click "Save"

The VPN goes up, and tls-crypt-v2 works!

HOWEVER, when I restart openvpn service, or restart PFSense, the VPN will not start, because the newline chars around the <tls-crypt-v2> tag have been stripped from the OpenVPN config, like so:

#only repeat logged warnings 3x:
mute 3<tls-crypt-v2>-----BEGIN OpenVPN tls-crypt-v2 client key-----
KEY_GOES_HERE_KEY_GOES_HERE_KEY_GOES_HERE_KEY_GOES_HERE
KEY_GOES_HERE_KEY_GOES_HERE_KEY_GOES_HERE_KEY_GOES_HERE
KEY_GOES_HERE_KEY_GOES_HERE_KEY_GOES_HERE_KEY_GOES_HERE
-----END OpenVPN tls-crypt-v2 client key-----</tls-crypt-v2>

In order to fix it, I have to re-enter the newlines, and re-save the config. This must be done every time I reboot.