Note, this is all on macOS on a Mac Mini M1 (aarch64); I expect things will be entirely different on Linux and Windows
It works the same for the other platforms.
- download fpcupdeluxe v2.4.0.fp
- set executable bits for the downloaded fpcupdeluxe file (chown)
- main window, set install path to a location where you have enough access rights (user space)
- main window, tab tags, right column lazarus version, select lazarus_4_0_RC_1, then press add tag
the textbox below will display "The tag with name [lazarus_4_0_RC_1 was added to the Lazarus sources list"
- main window, tab basics, set FPC version in left column to 3.2.2
- main window, tab basics, set Lazarus version in right column to lazarus_4_0_RC_1
- main window, press setup+
- advanced setting window, misc settings, checkmark "Docked Lazarus IDE", then press ok
- main window, press "Install/update FPC+Lazarus"
- confirmation dialog, press ok
- drink some beverage and/or eat a snack
- Done.
On first startup of Lazarus you should now be asked to select docked IDE