In order to get vbshout to work on 5.6.6 with PhP 8 you need to scroll up and pick up all the pieces of modifications and implement them all.
1) Download the latest vbshout from this thread.
2) Download from here
https://vborg.vbsupport.ru/showpost....&postcount=565
the jquery.tmpl.min.js file and put it in board/js/jquery
3) Make the quick fix modification noted in
https://vbulletin.org/forum/showpost...&postcount=601
4) Install Yilmaz's shoutbox.php
https://vborg.vbsupport.ru/showpost....&postcount=611
to /core/packages/dbtechvbshout/api/vbshout/shoutbox.php overwriting the existing file that is there.
Also I suggest changing
php_value max_input_vars
to 10000 if it is not already set to at least that. Otherwise when you try to save settings vbshout may not allow you to save them.
You should do all of the above and THEN add/import the xml file and run it.