I just noticed that after upgrading from 2.0.0 to 2.1.0 any calculated items that use the "last()" function without a "sec" or "#num" argument appear as NOT SUPPORTED reporting an error with the last() function.
My calculated item formula used to be similar to: last("host1:key[keyid]")+last("host2:key[keyid]")
This used to work in 2.0.0 and is how the examples of calculated items are shown in the documentation.
By changing the formulae to 'last("host1:key[keyid]",0)+last("host2:key[keyid]",0)' the items start working again.
I found ZBXNEXT-560 which might be related.
Not a big deal but could catch people out.