Wayne has some good suggestions but sometimes its not quite that simple. Should be but ....
Here is the depends line for my app when making debs -
Depends: libgtk2.0-0 (>= 2.6), libc6 (>= 2.14), libcanberra-gtk-module, appmenu-gtk2-module
From memory, libgtk2.0 will bring in libgdk2.0. And yes, your default Lazarus app will require GTK2.
More interesting is libcanberra-gtk-module, not used in my app, not listed by ldd as a dependency but if its not there, lots of complaints. Sigh.
And appmenu-gtk2-module is even more interesting ! We have found that Ubuntu 19.10 goes into some ill defined time out if its not present. Does not seem to be a problem on any other systems and I am eagerly waiting for U20.04 to see if it has the same problem. Its about connecting legacy GTK2 apps to the GTK3 DBus system, used for talking to menus, status bars, system tray.
But the issue is that older versions of Linux, such as U16.04, still a supported system and MXLinux, do not have appmenu-gtk2-module, so cannot use the same deb ! I suspect Canonical should have included appmenu-gtk2-module as a dependency of gtk2.0 on U19.10. The underlying problem is that GTK2 is not being installed by default any more on more and more linux systems so expect a lot of these sort of problems.
I am currently debating how to handle this in my next release, I don't want to have two different debs but feel bad about about cutting those users of old systems loose. I think I may drop mention of appmenu-gtk2-module but tell U19.10 users they also need to manually install it. Of course, with nothing officially using it, they will get prompted to remove it at some stage ....
And if we see the same problem in U20.04, a long term release ???
A better approach may be to tell users of newer systems to use a Qt5 version, the necessary Qt5 libraries are a lot smaller download than GTK2 and, perhaps more likely to be needed by other apps anyway. Perhaps. Your app maurobio will build fine with Qt5 if you use a bit more current version of Lazarus than 1.8.4
Oh, but don't use the Qt5 version on Fedora, it uses Wayland by default and that does not play nicely with Qt5.
There, you asked for some discussion !
Davo