https://askubuntu.com/questions/815471/unable-to-locate-package-pptd

https://github.com/Shipiloff69
https://www.syrog.ru/news/38/

https://www.veeble.com/kb/how-to-fix-e-unable-to-locate-package-error-on-ubuntu/

https://qdocs.qcri.org/space/pubkb/39583971/Ubuntu+-+How+to+configure+SonicWALL+NetExtender https://idroot.us/install-pptp-vpn-ubuntu-24-04/

https://www.ubuntuupdates.org/package/core/noble/main/base/pptp-linux

Package pptpd is not available. But is referred to by another package
This may mean that the package is missing. has been obsoleted, or
Is only avsilable from another source
package pptpd has no installation candidate

https://www.altlinux.org/L2TP_VPN_Client_Server
Consider Alternatives:  If pptp is truly not available, research and install a more modern   

https://gist.github.com/camsong/3721379
./configure make make install
