Set up SSL certs for local development. Only method that's worked for me. Tested on Ubuntu v20.x

default-apache-ssl.conf

#
# my default apache ssl conf, playground.test is the local site
#
Define servername playground.test
<IfModule mod_ssl.c>
    <VirtualHost _default_:443>
        ServerAdmin webmaster@localhost
        ServerName ${servername}
        DocumentRoot /var/www/html/${servername}

        <Directory "/var/www/html/${servername}">
            Order allow,deny
            Allow from all
            AllowOverride all
            Require all granted
        </Directory>

        ErrorLog ${APACHE_LOG_DIR}/${servername}-ssl-error.log
        CustomLog ${APACHE_LOG_DIR}/${servername}-ssl-access.log combined
        SSLEngine on

        SSLCertificateFile  /home/markhall/ssl-certs/${servername}.pem
        SSLCertificateKeyFile /home/markhall/ssl-certs/${servername}-key.pem

        <FilesMatch "\.(cgi|shtml|phtml|php)$">
                SSLOptions +StdEnvVars
        </FilesMatch>
        <Directory /usr/lib/cgi-bin>
                SSLOptions +StdEnvVars
        </Directory>

    </VirtualHost>
</IfModule>

default-apache.conf

#
# my default apache non-ssl conf, playground.test is the local site
#
Define servername playground.test
<VirtualHost *:80>
        ServerAdmin webmaster@localhost
        ServerName ${servername}
        DocumentRoot /var/www/html/${servername}

        ErrorLog ${APACHE_LOG_DIR}/${servername}-error.log
        CustomLog ${APACHE_LOG_DIR}/${servername}-access.log combined

        <Directory /var/www/html/${servername}>
                DirectoryIndex index.php index.html
        </Directory>
</VirtualHost>

Local SSL's For Development [Ubuntu]

# store all ssl's in home
mkdir $HOME/ssl-certs
cd ~/ssl-certs
mkcert -install

# playground.test is our test site
mkcert playground.test

# apache conf files
cd /etc/apache2/sites-available/

# create playground.test.conf
# create playground.test.ssl.conf

# edit hosts file with new local site
sudo /etc/hosts

# add line
127.0.0.1 playground.test

# enable the site in apache
sudo a2ensite playground.test.*

# reboot apache
sudo systemctl reload apache2

Updated mkcert as it's part of PopOS install, no need from brew install.