It's Wayland. FPC is available.
Edit : para below is too simplified. Firstly, GTK2 works with Wayland by, as much as it can, ignoring it. Secondly, the switch I mention is only necessary with Qtx.
Should work under Wayland but not nicely, you need to provide a command line switch, "--disableaccurateform", however, as a package install, you start Lazarus with "startlazarus" and can provide that switch there. But that command then calls "lazarus" and probably does not provide the switch ?? Don't know, I never use the packages, always build from source.
Depends: libgdk-pixbuf-2.0-dev (>= 2.21.0) but it is not installable or
libgdk-pixbuf2.0-dev (>= 2.21.0) but it is not installable
Wierd, my bookworm has libgdk-pixbuf-2.0 2.42.10 so should be available in the Pi repo.
Depends: libpango1.0-dev (>= 1.20) but it is not installable
I have libpango1.0-dev 1.50.12
similarly for all the other ones listed (I am sure). Lets be clear here, you obviously have GTK2 available and installed, whats missing are the -dev libraries. It would seem very, very surprising is RasPi people stripped out only some libraries. GTK2 needs to go but when it does it will be all or nothing decision.
I think you need to have a look at how apt list is configured, I don't think its pointing to a viable repository. You could post the result from "cat /etc/apt/sources.list" command.
Yes, building from source a Qt5 version (either directly or using fpcupdeluxe) is an alternative but if your repo is not configured, it will not work either. if you do try for Qt5, you must download newer libqt5pas1 libraries, the ones in bookworm will not work.
Edit : I am pretty sure the Raspi DE does not have an option to turn off Wayland, use it, ready or not (and its "not"). Sorry, I am traveling and don't have a RasPI available to test with.
Anyway, in summary, both GTK and Qt5/6 have dependencies that must be satisfied before you proceed to build or just run a prebuilt binary. Solve the repo problem first.
Davo