Template:thumbs/styles.css

/* float: right activates on min-width 720px */
@media screen and (max-width: 719px) {
  /* body.mw-mf: MobileFrontend only */
  body.mw-mf .t-thumbs-outer {
    margin: 0.6em auto;
    display: table;
  }
  body.mw-mf .t-thumbs-inner {
    display: flex;
    flex-flow: row wrap;
    column-gap: 0.6em;
    align-items: flex-start;
  }
}