I am on Fedora 31, I am trying to connect to a VPN that uses IKEv2 via strongswan. But I get [IKE] received NO_PROPOSAL_CHOSEN notify the error. I used the following tutorial https://www.securevpn.pro/eng/setup/linux-ikev2-vpn?url=eng%2Fsetup%2Flinux-ikev2-vpn to install the VPN. Multiple websites mention certificates, but since I am on the client-side, do I need to create certificates? should I configure someting specifically?
Any hint, idea, solution is welcome.
Without detailed log from at least your end it is not possible to be sure what is going on. However, checking the guide which you referenced in your question, I think I might have spot the issue.
In the step 7 of the guide, there is an instruction to customize cipher proposals to a single specific one. The specific cipher proposal might not be supported by the other end. I suggest to remove this limitation, i.e. to uncheck the checkbox. I took a screenshot of the step 7 from the guide and marked the checkbox with a red arrow, see below.