I wonder if there is a way to have it off-line on a disk for example, for the case it will cease operation for any reason.
Yes, its possible

Because of GDPR i would need to remove all user identification
- email address-IP address etc

But its possible to run the whole system as a virtual machine under virtual box or xen or similar

Though i will keep the forum online if it is within my power.
I dont think i can devote time to this in March
But in April. I could certainly do something.