Finally. Really happy with it, except that the explorer/trending and trending page hasn't been updated yet. I hope that will follow to protect my eyes from that brightness contrast at night and in the morning.
@-moz-document domain("github.com") {
.dashboard .js-all-activity-header + div {
background-color: inherit !important;
border: 1px solid var(--color-border-secondary) !important;
}
.dashboard-rollup-items .body {
border-top: 1px solid var(--color-border-secondary) !important;
}
}