Ubuntu's symfony 5.4 is not compatible with php < 8

As it is being discussed in https://github.com/phpmyadmin/phpmyadmin/issues/17523,
the symfony package is patched to support newer PSR versions than the ones available in Debian (and than the ones ussported by symfony 5.x).

This results in non_php_<_8_compatible return types being added to some symfony packages. When these are invoked with php 7.4, it results in errors being raised, which is the case for trying to run phpmyadmin with a php7.4 runtime.

Possible solutions include bumping the minimum php requirement for those packages (and possibly update documentations where needed) or re-assessing the patches for PSR compatibility.