Joomla 4

I've problems to install vers. 3.9.8 to Joomla 4.
It appears following answer: Call to undefined method Joomla\CMS\Installer\Adapter\ComponentAdapter::get().

Has anyone an idea?
I hope, i get answers!
Thanks

Fox Contact has unfortunately not been further developed since 2018 and is not even compatible with joomla 3.10.
Much to the displeasure of many users and there is also no opinion from the developer, which is also a shame.
We have also switched to a contact form component.
Maybe one day that will change again and it will be further developed.

I have de same problem. Any solution ?

Unfortunately, there is no solution to this yet!
Maybe Demis Palma will speak up one day! I hope so!

I also want to remove the link to foxcontact in my backend, is there no solution from the developer?

You can remove the fox contact tables from your data base. I have a note that on updating to 3.9.19:

Update: Could not open update site #__ "Foxcontact update site", URL: http://www.fox.ra.it/phocadownload/foxcontact.xml
So I deleted the update site.

I uninstalled all fox contact extensions (3.4.3 and 3.4.4) then dropped the table "#__foxcontact_enquiries" in phpMyadmin.

That was around December 2021 at the same time I was getting the awful Logman and Extman out of the database and off the site.