"Resonance" frequency (im(S11) = 0) is about 5 GHz, but radiation resistance is > Z0, not matched. In practice, the matching may be sufficient for the intended antenna purpose.,
If we can ignore copper loss, dielectric loss, matching element loss, guided loss, etc., real(Zin) is equal to radiation resistance.
Even if loss is not zero, real(Zin) is close to radiation resistance in many cases.
Here I treat object including matching elements as antenna, although I don’t think matching should be included in antenna.
Yes, in an ideal world things are ideal, which makes it simple.
In my work on antenna simulation, I can separate radiation resistance from losses, and losses are often a major influence.
For patch antennas on FR4, we have large dielectric loss.
For electrically small antennas, as used in many devices today, we often have radiation efficiencies of 50% or less, so that radiation resistance is much smaller than input resistance.