You can donate to OpenSSH[0], whose "funding is generally done via the same donation framework" as the rest of OpenBSD, to which you can donate either directly[1] or via the OpenBSD Foundation[2]. If you're serious about donating obviously please check that these links are legitimate and I'm not a scammer. (I'm not affiliated with OpenBSD in any way.)

[0] https://www.openssh.com/donations.html

[1] https://www.openbsd.org/donations.html

[2] https://www.openbsdfoundation.org/donations.html