Instalando o SqlSrv para acesso ao MSSQL via PHP com APACHE no Ubuntu Server 20.04 LTS.
apt -y install unixodbc-dev gcc g++ make autoconf libc-dev pkg-config php-pear php-dev
curl -s https://packages.microsoft.com/keys/microsoft.asc | sudo apt-key add -
bash -c "curl -s https://packages.microsoft.com/config/ubuntu/20.04/prod.list > /etc/apt/sources.list.d/mssql-release.list"
apt update
ACCEPT_EULA=Y apt -y install msodbcsql17 mssql-tools
pecl install sqlsrv; pecl install pdo_sqlsrv
bash -c "echo extension=sqlsrv.so > /etc/php/7.4/apache2/conf.d/pdo_sqlsrv.ini"
service apache2 restart
Fonte: https://magnus.tech/sqlsrv-on-php-7-4-and-ubuntu-20-04/