Create a new catalogue, sign in, set it to sync, then close it and never open it again. From now on LR Sync will see you are using a catalogue that isn't the one you synced, and so it shouldn't display the message.
I don't know the educational version, but my understanding is that there is no cloud space but you can sync from your catalogue as normal, meaning you can easily get pictures onto your phone to show people or to do little tweaks on the move. Once you have this, it becomes very convenient. The lack of cloud space means you can't sync originals, but when you sync from Classic it only uploads "smart previews" which don't count against the cloud space allocation.
I believe there is 20GB of cloud storage with Student and Teachers version Creative Cloud pricing and membership plans | Adobe Creative Cloud
There's a dedicated tab for Student and Teachers at above link.
Thanks for your tipp; it sounds as if it could work. However, not only do I have an educational version, but my whole laptop belongs to the university (my employer). The lightroom version I have is part of an image which is used on computer pools for students as well (which is the reason why I don't have cloud storage space). Long story short, it was purchased and installed with an adobe ID that is handled by our tech support, meaning I can't sign in, as I don't have the password ... any other ideas? If not I'll have to drop by tech support I suppose.
I suspect you'll need to speak to the university tech support
Tell them to create that synced catalogue that I described in my first post. But signing in also validates the licence to run LR, so in 30 days you would need to do so again.
Thanks Ian too.