<template>
  <view>
    <page-meta :page-style="popupOpen ? 'overflow:hidden;' : ''" />

    <view class="content">
      <!-- 底部可滚动内容 -->
      <scroll-view scroll-y style="height: 500rpx;">
        <view v-for="i in 30" :key="i">内容 {{ i }}</view>
      </scroll-view>
    </view>

    <u-button @click="popupOpen = true">打开弹窗</u-button>

    <u-popup v-model="popupOpen" mode="bottom">
      <view class="popup-box">
        弹窗内容
        <u-button @click="popupOpen = false">关闭</u-button>
      </view>
    </u-popup>
  </view>
</template>

<script>
export default {
  data() {
    return {
      popupOpen: false
    }
  }
}
</script>

关键代码：

page-meta :page-style="popupOpen ? 'overflow:hidden;' : ''"