After switching to the Overview tab, Scheduler throws this debugging warning in Moodle 3.11.8:

user_picture::fields() is deprecated. Please use the \core_user\fields API instead.

    line 256 of /lib/outputcomponents.php: call to debugging()
    line 111 of /mod/scheduler/datelist.php: call to user_picture::fields()
    line 86 of /mod/scheduler/view.php: call to include()

user_picture::fields() is deprecated. Please use the \core_user\fields API instead.

    line 256 of /lib/outputcomponents.php: call to debugging()
    line 123 of /mod/scheduler/datelist.php: call to user_picture::fields()
    line 86 of /mod/scheduler/view.php: call to include()