We need to locate the php.ini file on the Ubuntu Server and then switch to that directory.

:~$ cd /etc/php/8.1/apache2/
:~$ /etc/php/8.1/apache2/$
:~$ /etc/php/8.1/apache2/$ ls
:~$ /etc/php/8.1/apache2/$ php.ini

Edit php.ini using vim or nano.

:~$ vim php.ini 

Within the php.ini file, locate and modify the following settings to read as follows, and enable date.timezone by deleting the leading semicolon ';date.timezone ='

memory_limit = 512M
upload_max_filesize = 500M
post_max_size = 500M
max_execution_time = 300
date.timezone = America/New_York

Here is another author's similar list for making changes. For the basic nextcloud deployment, change the default options using the following configuration.

file_uploads = On
allow_url_fopen = On
memory_limit = 512M
upload_max_filesize = 500M
post_max_size = 600M 
max_execution_time = 300
display_errors = Off
date.timezone = Europe/Amsterdam
output_buffering = Off

Save and close the php.ini file when you are finished. Then, start the Apache and MySql service and enable them to start after system reboot with the following commands:

sudo systemctl reload apache2
sudo systemctl start apache2
sudo systemctl start mysql
sudo systemctl enable apache2
sudo systemctl enable mysql

These commands will run like the following.

:~$ sudo systemctl reload apache2
[sudo] password for user:
        OR
:~$ sudo systemctl start apache2

:~$ sudo systemctl start mysql
:~$ sudo systemctl enable apache2
Synchronizing state of apache2.service with SysV service script with /lib/systemd/systemd-sysv-install.
Executing: /lib/systemd/systemd-sysv-install enable apache2
:~$ sudo systemctl enable mysql
Synchronizing state of mysql.service with SysV service script with /lib/systemd/systemd-sysv-install.
Executing: /lib/systemd/systemd-sysv-install enable mysql
:~$

Use Vim to open php.ini again to enable opcache extension and configure its options and behavior.

cd /etc/php/8.1/apache2/
vim php.ini

First, uncomment the 'zend_extension=opcache' option to load the opcache extension. Uncomment means to remove the leading semi-colon “;” at the front of the line containing ';zend_extension=opcache'

Before
;zend_extension=opcache

After (uncommented)
zend_extension=opcache

Now, move down to the '[opcache]' section of the php.ini file and add the following configuration. Basically, just find the appropriate line and uncomment the line by removing the leading ';' semi-colon. You can safely ignore the . . . lines in the code box below.

[opcache]
...
....
.....
opcache.enable = 1
opcache.interned_strings_buffer = 8
opcache.max_accelerated_files = 10000
opcache.memory_consumption = 128
opcache.save_comments = 1
opcache.revalidate_freq = 1

Press ESC button to exit the INS mode of Vim and save the configuration by entering :w [enter], then exit by entering :q!

Now restart the apache service to apply new changes using the command below.

sudo systemctl restart apache2