client/src/app/shared/shared-user-settings/user-interface-settings.component.html
<form (ngSubmit)="updateInterfaceSettings()" [formGroup]="form">
<div class="form-group">
<label i18n for="theme">Theme</label>
<div class="peertube-select-container">
<select formControlName="theme" id="theme" class="form-control">
<option i18n value="instance-default">{{ instanceName }} default theme ({{ getDefaultInstanceThemeLabel() }})</option>
<option i18n value="default">{{ getDefaultThemeLabel() }}</option>
<option *ngFor="let theme of availableThemes" [value]="theme.id">{{ theme.label }}</option>
</select>
</div>
</div>
<input *ngIf="!reactiveUpdate" type="submit" class="mt-0" i18n-value value="Save interface settings" [disabled]="!form.valid">
</form>