Lazarus is very up to date with the latest versions, for example version 3.2 (current).
Lazarus is compatible with codes made in Delphi, sometimes requiring some adjustments mainly because you can use the {$mode delphi} directive at the beginning of all units.
I believe that you would initially need to migrate only the front-end components. Of course I don't know the extent of the entire Unigui package.
I have already participated in software migration from Delphi to Lazarus and when we use the Delphi directive the work becomes much faster.
example of using the directive:
unit Test Unit;
{$mode delphi}
interface
uses
...
