Use # instead of v-slot:

src/client/app/desktop/views/home/user/user.home.vue

@@ -5,7 +5,7 @@
 	<!--<mk-calendar @chosen="warp" :start="new Date(user.createdAt)"/>-->
 	<div class="activity">
 		<ui-container :body-togglable="true">
-			<template v-slot:header><fa icon="chart-bar"/>{{ $t('activity') }}</template>
+			<template #header><fa icon="chart-bar"/>{{ $t('activity') }}</template>
 			<x-activity :user="user" :limit="35" style="padding: 16px;"/>
 		</ui-container>
 	</div>