Question Migrate and clean old database

Hello, everyone,
We have a Joomla 3.9.24 site that uses Kunena 5.0.0.We are building a new site from scratch and will not be updating the old one. The new site will be based on Joomla 5 and YOOtheme Pro.The customer asked if it’s possible to transfer the old topics and posts from the current site to the new one. I found that upgrading to Joomla 4 and updating the Kunena component is a recommended step, but we don’t want to build the new site as an upgrade of the old one. This is why I’m asking if it’s possible to handle the data migration directly.This is not a large site; the forum is used like a simple guestbook. There are no rankings, moderators, or special features, but it does have over 10,000 spam entries.Does anyone have suggestions for cleaning the posts which are already in the database?

Thank you in advance
Peter

does have over 10,000 spam entries

How do you idenfify those entries? Normally spam entries should be removed. Either by blocking the users or by deleting the entries manually.

If Kunena is only used as a guestbook, there will probably also be writing rights for guests. If spam posts have been regularly deleted, these posts can be permanently deleted from the trash (Backend -> Kunena -> Trash -> Purge items). This will remove these posts from the database too.
However, if these posts have never been deleted, you will have to search the ‘Guestbook/Forum’ manually to delete them.

Afterwards you can import the Kunena tables into the new website database and then simply install Kunena 6.x over them. If there are also posts in the forum from registered users, you would also have to import the Joomla user tables into the new database. But I think you will do this anyway, as the Joomla users will remain the same in the new website.