// If you look at [this great answer](https://stackoverflow.com/a/29733127/1548895) you'll notice that the only cross-browser way (without 2 line break limit) is inserting `100%`\-width empty blocks ("line-breaks"). So for similar markup this will look like

.flex {
  display: flex;
  flex-wrap: wrap;
  border: 2px solid red;
}

.line-break {
  width: 100%;
}