In the Lazarus IDE you can set particular compiler options as the default settings.
Choose the Project->Project Options... menu (Ctrl+Shift+F11 is the default shortcut) to display the Options for Project: xxx dialog.
The default mode set for all project units is shown under
Compiler Options
Parsing
in the treeview on the left.
You want the dropdown labelled "Syntax mode{-M, {$MODE}}"
You want to ensure the dropdown is set to
"Object Pascal - default (-MObjFPC).
If you tick the checkbox at the bottom labelled "Set compiler options as default" before clicking the OK button, this will make sure that new projects are populated with skeleton code including your preferred mode.
If you still get the 'wrong' mode in new units, it's also worth checking the setting in your fpc.cfg file, in case this conflicts.