el-card:
<el-card class="transparent-card">
...
</el-card>
.transparent-card {
background-color: transparent !important;
border: none !important;
}
el-table:
:deep .el-table,
.el-table__expanded-cell {
background-color: transparent;
}
:deep .el-table tr {
background-color: transparent !important;
}