PHP 7.4 has end of life on 28 November 2022, so it won't get security updates any more. I suggest to follow my instructions to avoid 500 Errors on your joomla 3 or 4 sites when updating to PHP 8.0:

1. backup your site
2. set Global configurations/Server/Error reporting to Maximum
3. Search for updates, and update the joomla extensions and joomla to the latest 3.10.x or 4.x
4. Test your site
5. Update PHP to 8.0 (not 8.1), e.g. in cpanel if you have access to it
6. Increase the php memory_limit to 128M, e.g. in cpanel or in a php.ini file
7. test your site
8. if you see an error message, investigate which joomla extension caused it. If it's a memory size problem, try to increase the php memory_limit, or disable that extension. Maybe you need to switch back to php 7.4 to be able to log in to the admin area if you want to disable an extension. Then start again from number 5.

After testing switch back Global configurations/Server/Error reporting to None.

The best joomla 4 templates of ours were released today, you can download or purchase them from the links below:

• a4joomla-best-free
• a4joomla-best
• a4joomla-dark-free
• a4joomla-dark

If you bought the joomla 3 version of one of the two pro templates, then just log in, and click on YOUR ORDERS, then Action/Details, and in the Files column you should be able to download the new joomla 4 templates: a4joomla-best4.zip or a4joomla-dark4.zip .

Migration from joomla 3 to joomla 4

First read the official instructions of this mini migration by clicking here.  Then, let's say you used the a4joomla-best joomla 3 template. These are my template related instructions if you don't want to lose your template parameter settings, and template modifications:

1. You have joomla 3.x, now backup your site e.g. with Akeeba Backup
2. Save the old template, especially your user.css if you have one in the css folder
3. Update joomla to joomla 3.10, clear the cache if you have, and test the site in incognito mode of your browser
4. Update the extensions, and test the site again
5. Set Protostar to the default template
6. Update joomla 3 to joomla 4, and test the site, now you should see the Cassiopeia template.
7. Remove the a4joomla-best folder in an FTP client, or delete the folders and files of the template from the admin area if possible. Thus we keep the old template settings in the database, and we remove just the old template files and folders.
8. Install a4joomla-best4.zip! Now you will have two template styles with the same name: a4joomla-best. Try to set them to default, and test the site to see, which one contains your old template parameter settings. Keep that one, and you can delete the other template style.
9. Update other extensions, test the site, etc.

Some CSS classes should be replaced if you hide some of your modules on mobile with css classes in the "Module class suffix". You can find the new css classes for hiding modules here. You can hide modules on different display sizes: xs=extra small, sm=small, md=middle, lg=large, xl=extra large, xxl=the largest.