Introduction
The images opposite show the principal requirements for J4, J5 and J6. The main change in these is that the minimum PHP level for J5 is now 8.1 and for J6 it is 8.3.



Getting to Joomla Next
Next at top right Click on the
So again click on the

If there is no update available then exit by clicking on the
button at the top right.
Compatibility Check
If an update is available
this instigates the 'checking' process.
It typically brings up the view as shown opposite. Note that the reqirements for Joomla 4, 5 and 6 are similar.
So click on the

Actually the jD System Plugin is OK.
Apparently it is the way the system plugin is coded so it apparently does not totally conform to Joomla practice.
If you scroll further down you will see a report as shown below.
If you now scroll down to the bottom of the report you will find
This then gives an 'Are you Sure Message' where you need to click on OK. The 
Updating
This will start the Update.
After a little time it becomes

Note that the update channel has been reset to "Default" so when the next update to Joomla becomes available it will be notified in the normal way.
That is click on the

