Hi Ally,
to show the timestamp and last-post info on mobile devices / smartphones you could do a little change to the forumview.htm file like that:
OPEN
forumview.htm
FIND
(around line 185)
Code
<span class="uk-text-muted cf-text-micro">
[ {$LANG.topic_created}: {$TOPIC_LIST[topics].topic_created} {$LANG.by} {if $TOPIC_LIST[topics].topic_fst_poster_id > $ANONYMOUS}<a href="{rewrite mode='user' id=$TOPIC_LIST[topics].topic_fst_poster_id title=$TOPIC_LIST[topics].topic_fst_poster}">{/if}<span class="uk-text-bold cf-gcolor-{$TOPIC_LIST[topics].topic_fst_poster_color}">{$TOPIC_LIST[topics].topic_fst_poster}</span>{if $TOPIC_LIST[topics].topic_fst_poster_id > $ANONYMOUS}</a>{/if} ]
AFTER ADD
(but still before the closing </span> though)
Code
<span class="uk-visible-small"><br />[ {$LANG.index_lasttopic}: <a href="{rewrite mode='post' id=$TOPIC_LIST[topics].topic_lst_post_id title=$TOPIC_LIST[topics].topic_lst_subject}" rel="nofollow"><b>{$TOPIC_LIST[topics].topic_lst_subject|truncate:30:'…':true:false}</b></a> {$LANG.by} {if $TOPIC_LIST[topics].topic_lst_poster_id > $ANONYMOUS}<a href="{rewrite mode='user' id=$TOPIC_LIST[topics].topic_lst_poster_id title=$TOPIC_LIST[topics].topic_lst_poster}">{/if}<span class="uk-text-bold cf-gcolor-{$TOPIC_LIST[topics].topic_lst_poster_color}">{$TOPIC_LIST[topics].topic_lst_poster|truncate:20:'…':true:false}</span>{if $TOPIC_LIST[topics].topic_lst_poster_id > $ANONYMOUS}</a>{/if} @{$TOPIC_LIST[topics].topic_last_post_time} ]</span>
This would add the info you see on every other viewport on the right as extra-line on mobile devices. But without the avatar image (because of the space needed on mobile devices). It will also add a link to jump to the last post of the topic instead of the first page like when you click on the title. Beside that it will not use additional space on the other viewports where you have that information on the right side anyway.
Hope this helps you.
Sincerely,
Chris