Having written the same application in both LCL and MUIClass, I just wanted to put a couple of lines out there for anyone else looking to get started in AROS app development in FPC.
LCL is the easiest to get going with, as you're just using the regular FPC/Lazarus process. You put things on a form, create your handlers, etc.
Easy peasy.
Unfortunately there are a number of bugs. ALB42 created the LCL implementation and told me that some of the bugginess comes from the fact he had to use a custom layout to let you place components in the LCL way, aligning things and so on.
It works fine for simple applications. AWeather is borderline as it contains multiple panels and formatting. It mostly works but due to the multiple panels there are graphic issues that are not solvable by an app developer.
MUIClass is a more raw implementation of MUI/Zune for FPC, also created by ALB42.
You work without the LCL middle layer, making the application smaller and much faster (Usable on m68k)
You have MUCH less control over the GUI compared to LCL as you have to follow the MUI way of things. Practically it means your GUI will be place based on parent ownership and not window-based positions.
The application will look much more Amiga like.
MUIClass so far doesn't really have bugs like LCL has, it has worked out quite nicely for AWeather.
When I ran into an issue not knowing how to implement an image, I emailed ALB and he had an example made up over night for me.
Because you can't use the LCL you also don't get the wonderful GUI design capabilities of Lazarus. Luckily ALB also created MUIIDE, a tool for designing GUI's in AROS, you can then export it as source code and start filling in all your practical code.
Without MUIIDE you'd be stuck in the dark ages of blindly creating IDEs and testing.
It has some quirks but they're not that bad. For example when working with pages, when you make a change it will reset the page to the first one, so if you're working on the second page you'll do a lot of clicking the tab, lol.
I'll write up a full tutorial at some point, but I wanted to put a little starter-information out there and let people know about the options
I know people use the Docker image for compiling or the premade VM, I used FPCUpDeluxe to install the cross compilers and it's working well.
Installing MUIClass is easy, just download the lib and include in your path (Tutorial coming at some point)
https://github.com/alb42/MUIClass