Pues te esta haciendo falta instalar php-mcrypt, las librerías de curl y las librerías gd entre otras.
Insertar CODE, HTML o PHP:
apt-get install php7.3 php7.3-cli php7.3-common php7.3-opcache php7.3-curl php7.3-mbstring php7.3-mysql php7.3-zip php7.3-xml php7.3-gd
Y reiniciar apache... Revisa el php.ini que no tenga rutas incorrectas por el cual estés cargando librerías de rutas inexistentes.
Instalado, sigue sin funcionar, error.log_:
PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php/20151012/gd.so' - /usr/lib/php/20151012/gd.so: cannot open shared object file: No such file or directory in Unknown on line 0
PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php/20151012/curl.so' - /usr/lib/php/20151012/curl.so: cannot open shared object file: No such file or directory in Unknown on line 0
PHP Warning: Module 'mcrypt' already loaded in Unknown on line 0
PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php/20151012/gd.so' - /usr/lib/php/20151012/gd.so: cannot open shared object file: No such file or directory in Unknown on line 0
PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php/20151012/curl.so' - /usr/lib/php/20151012/curl.so: cannot open shared object file: No such file or directory in Unknown on line 0
PHP Warning: Module 'mcrypt' already loaded in Unknown on line 0
PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php/20151012/gd.so' - /usr/lib/php/20151012/gd.so: cannot open shared object file: No such file or directory in Unknown on line 0
PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php/20151012/curl.so' - /usr/lib/php/20151012/curl.so: cannot open shared object file: No such file or directory in Unknown on line 0
PHP Warning: Module 'mcrypt' already loaded in Unknown on line 0
[Mon Jun 17 20:48:17.315393 2019] [mpm_prefork:notice] [pid 25102] AH00169: caught SIGTERM, shutting down
[Mon Jun 17 20:48:18.421784 2019] [suexec:notice] [pid 5593] AH01232: suEXEC mechanism enabled (wrapper: /usr/lib/apache2/suexec)
[Mon Jun 17 20:48:18.468288 2019] [mpm_prefork:notice] [pid 5594] AH00163: Apache/2.4.18 (Ubuntu) SVN/1.9.3 mod_fcgid/2.3.9 OpenSSL/1.0.2g configured -- resuming normal operations
[Mon Jun 17 20:48:18.468316 2019] [core:notice] [pid 5594] AH00094: Command line: '/usr/sbin/apache2'
PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php/20151012/gd.so' - /usr/lib/php/20151012/gd.so: cannot open shared object file: No such file or directory in Unknown on line 0
PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php/20151012/curl.so' - /usr/lib/php/20151012/curl.so: cannot open shared object file: No such file or directory in Unknown on line 0
PHP Warning: Module 'mcrypt' already loaded in Unknown on line 0
Por otro lado en /etc/php/ tengo 5.6/ 7.0/ 7.1/ 7.2/ 7.3/
No se si es correcto esto y en cual deberia editar el php.ini