Atlaskit (their UI framework) is open source.

It is very enlightening. Try using their editor component to display the text of one of your Jira comments and making it display attachments.

find or create an installation and examine how the database is put together

Try to use one

Try using two of them connected together.

In order to do that, one would have to try to connect one to the other, which is usually sufficient.

First you need a fire starter, which in this case must be made out of bills valued 100 USD each or greater. It'll take quite a few to light the Datacenter licenses that are the now the only on-prem tier on fire...

So... you do not, in fact, have an answer to the question?

Lacking humor I see.

My point is that it is experience acquired from managing these for a decade. If you wish to acquire this experience you need to run it, which is now even costlier than it used to be.

Actually using these products suffices. Especially confluence, which regularly reduces me to a stream of particularly foul profanity.