IPK files are not installed via the server, they are installed by using a FTP program, like Filezilla, transferring them to your tmp folder, then installing them through your receivers menu, providing that they are suitable for the newer python 3 images, like OpenBh 5.1.
You should be going into your receivers menu, select Plugins, then press the Green Button, on your remote, to Download plugins, once completed scroll down to softcams and select the oscam of your choice, probably Oscam latest, as 50_lire posted.
Once installed you exit the menu, press the Blue Button, on your remote, select Oscam, and OK, then Oscam latest should appear in your etc/tuxbox/config folder.