Yes, the hub is identical
Same 5x114.3 PCD and same 67.1 mm centre bore: wheels from Kia EV3 bolt on and centre on Mazda RX-8 without rings. You still need to check the offset and tyres, detailed below.
≈: width estimated from the original tyre size.
Wheel by wheel: offset and tyres
Each original wheel from Kia EV3 is compared with the one from Mazda RX-8 of the same diameter: how much closer the wheel gets to the shock absorber or how far it sticks out of the wheel arch, and whether the tyre keeps the same overall diameter.
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7Jx17 ET48 · 215/60R17 — Check on the car
Compared with the original ≈6.5Jx17 ET50 on Mazda RX-8: shock absorber side +4.3 mm, wheel arch side +8.3 mm, tyre diameter +4.9 % : fit it with the original tyre size of Mazda RX-8 (205/55R17), not that of Kia EV3.
Comparison for guidance only (estimated width). Check in detail
Before fitting the wheels
An identical hub is not enough: offset, width and diameter change the position of the wheel, and larger calipers can touch a smaller wheel. Original wheels often use bolts or nuts with a specific seat: keep the fixings intended for the wheel, with the thread of Mazda RX-8 (Ecrous - 12x1.50), tightened to the torque shown on its vehicle page. Finally, check that the size is among the approved fitments for your vehicle. This comparison is for guidance only: have the fitting approved by a professional.
And the other way round: wheels from Mazda RX-8 on Kia EV3?