PhpBB3 BBCodes

Install this one as an extension. It will add an extra stylesheet with the code for se_square

Use the same EXT and create a style folder with the name of your style.
Then copy the css file to the new folder.
Purge cache and see if it does the trick

ITs a complicated theme. You need to ask the author.
IMHO the icons look much better in that theme than the ones I use here

Not phpBB but PHP
Anyway, probably lower than 8
Try forumgoal version 1.1.4 - it supports PHP 7.1

Extension Name: Last Active in Topic
Author: Stoker
Extension Version: https://img.shields.io/badge/version-0.9.2_dev-FFBF00
Requirements:

Extension Description:
Last Active in Topic will display users last active time in topics. Permissions to view hidden users are respected.

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