Lazarus is pretty much a free and open source Delphi (yes there are differences but they do not matter much) and really not any different in terms of difficulty compared to it.
(if the time stamp doesn't work, skip to 11:32, the previous ~11 minutes are me downloading, compiling it and configuring it - not 100% necessary on Linux and on Windows i never do that as the installer is a classic wizard-based one, but as i write on the video, i prefer to compile it when using it on Linux - also note that on Windows you do not need to install FPC as it comes bundled with Lazarus, it is really just running the installer, double clicking the desktop icon and you're ready)
https://www.lazarus-ide.org/
You can see it in action under Linux here where i make a simple puzzle game:
https://youtu.be/s_01Xhd2EJM?t=692
(if the time stamp doesn't work, skip to 11:32, the previous ~11 minutes are me downloading, compiling it and configuring it - not 100% necessary on Linux and on Windows i never do that as the installer is a classic wizard-based one, but as i write on the video, i prefer to compile it when using it on Linux - also note that on Windows you do not need to install FPC as it comes bundled with Lazarus, it is really just running the installer, double clicking the desktop icon and you're ready)