Vuetify v3 component override. Example here with VBtn

Button.vue

<script setup lang="ts">
import { computed } from 'vue'
import { VBtn } from 'vuetify/components'

type VBtnProps = InstanceType<typeof VBtn>['$props']

interface Props extends /* @vue-ignore */ Omit<VBtnProps, 'variant' | 'color'> {
  variant: 'primary' | 'secondary'
}

const props = withDefaults(defineProps<Props>(), {
  variant: () => 'primary'
})

const color = computed(() => {
  switch (props.variant) {
    case 'primary':
    default:
      return 'purple'
    case 'secondary':
      return 'black'
  }
})

const vuetifyVariant = computed(() => {
  switch (props.variant) {
    case 'primary':
    default:
      return 'flat'
    case 'secondary':
      return 'outlined'
  }
})
</script>

<template>
  <v-btn v-bind="$attrs" :variant="vuetifyVariant" :color="color" />
</template>

<style scoped></style>