Comment # 5 on bug 1219920 from Stefan Hundhammer

It will depend in how many places this validation is actually needed.

If it's only for this yast2-dns-server, we need to consider that it's already
dropped for Factory / Tumbleweed and future products, supported only for the
remaining life time of SLE-15 SPx and Leap 15.x. Since during all the time
until just now nobody asked for this, it can't be that important, so we
probably shouldn't invest too much into it.

If we also need it for many other networking-related YaST modules, that's
different; but only if it's about creating NEW domain names, not connect to an
existing one. If you need to use an existing domain with such a name, you don't
have much choice. But if you are creating a new one, that's different.