Hi Ralf,
I haven't created a custom addon for PageBuilder, but since it requires a Joomla plugin, you will need to update a number of the files/classes to match J4 conventions.
Checking some of Pagebuilder's J4 addons will help with this.
There's a distinct likelihood that the addons now use namespacing too, if following J4 conventions.
A quick look at the tutorial, I see some obvious changes that will be required:
REF: step 2 of the JoomShaper guide
- Re-write the PHP plugin class to match the Joomla 4 plugin signatures. N.B. [PlgSppagebuilderDemo] extends JPlugin will need to be replaced with PlgSppagebuilderDemo extends CMSPlugin. Naturally, if namespacing is used, instead of include/require statements, you'll replace these with the appropriate use statements.
- The XML manifest file will require updating to match J4. Again, looking at any existing addons will help with this, but your
extension version="3.8" will of course need updating.
This should get you most of the way, I hope.
Finally, there's an example plugin for Joomla 4 on the Joomla Wiki here, that I hope will provide additional context for #1 above.
Hope it helps,
Gez