danclarkie If you want to run composer with a different version of PHP, then you can do that by passing the composer executable to whichever PHP version, like so:
php81 <path to composer> <your commands here>
You can also run the following commands on the server via SSH:
mkdir -p ~/bin
ln -s /usr/bin/php81 ~/bin/php
export PATH=$HOME/bin:$PATH
That will create a "php" executable symlink in your ~/bin directory linked to php81
. The PATH setting will make it the first "php" on the search path, i.e., when you run "php", it will use that instead of the system default.