Aleksei Shchekochikhin released aPolyvoks for free back in March of 2019, and literally no one gave a single shit about it. The App Store lists the app's release as Mar 19, 2019 and I only just found out about it thanks to The Sound Test Room in March 2021. That is because in March of 2021, the app suddenly got a couple of updates adding AUv3 to this completely free emulation of the famous Soviet synthesizer Polivoks.
aPolyvoksOld style synth inspired by famous soviet POLIVOKS synth. Two separated freely controlled generators. Crossmodulation and FM. Noise additive generator.
What's New in v1.4:AUv3 extension previous iOS versions support fix
What's New in v1.3:AUv3 extension added
Doug from The Sound Test Room deserves full credit on this freebie find!