Install this on your 3.8 board, it will work.
https://vborg.vbsupport.ru/showthread.php?t=149377&highlight=username+change
Then, In your MEMBERINFO template.
Search for:
<div id="profile_tabs">
Add ABOVE:
<!-- Username History -->
<if condition="$show['username_history']">
<table class="tborder" cellpadding="6" cellspacing="1" border="0" width="100%" align="center">
<tr>
<td class="tcat">$vbphrase[unreq_un_hist]</td>
<td class="tcat"></td>
<td class="tcat"></td>
<td class="tcat"></td>
</tr>
<tr>
<td class="thead">$vbphrase[unreq_date]</td>
<td class="thead">$vbphrase[unreq_original]</td>
<td class="thead">$vbphrase[unreq_new_un]</td>
<td class="thead">$vbphrase[unreq_status]</td>
</tr>
$username_history_bit
</table>
<br />
</if>
<!-- / Username History -->
Doing this will show the username history like this: https://nacc.club/member.php?u=23