I have a few sites still running Concrete version 18.104.22.168. Does anyone know what version of PHP it requires and if it can upgrade to php 7.4? Thanks so much for your help.
You will need to update the site to 22.214.171.124 from the legacy github. That is just a code swap, there are no changes to database tables.
The 5.6.4 code is compatible with php7.4.
Some of your application code and addons may not be compatible. So you may have to fix them.
Take a files and database backup before starting and be prepared to revert if necessary !!!