From v3 to v4

All models now need to define a getActivitylogOptions() method to configure and return the models options as a LogOptions instance.
To control what attributes are logged, instead of defining a $logAttributes property this is defined in the getActivitylogOptions() method using the logOnly() method of LogOptions.
The getDescriptionForEvent() method is no longer used to customize the description. Instead, use the setDescriptionForEvent() method for LogOptions class.
When customizing the log's name instead of defining a $logName property, call the useLogName() method when configuring the LogOptions.
Instead of the $ignoreChangedAttributes property the dontLogIfAttributesChangedOnly() method should be used.
If you only need to log the dirty attributes use logOnlyDirty() since the $logOnlyDirty property is no longer used.
For instances where you do not want to store empty log events use dontSubmitEmptyLogs() instead of setting $submitEmptyLogs to false.
When you use a * (wildcard) and want to ignore specific elements use the dontLogIfAttributesChangedOnly() method instead of the $logAttributesToIgnore property.

From v2 to v3

if you are using a custom Activity model, you should let it implement the new Spatie\Activitylog\Contracts\Activity interface
the preferred way to get changes on an Activity model is through the changes property instead of the changes() function. Change all usages from $activity->changes() to $activity->changes
the activity relation of the CausesActivity trait has been renamed to actions. Rename all uses from $user->activity to $user->actions
the activity relation of the LogsActivity trait has been renamed to activities. Rename all uses from $yourModel->activity to $yourModel->activities.
the deprecated loggedActivity relation has been removed. Use activities instead.
the HasActivity trait has been removed. Use both CausesActivity and LogsActivity traits instead.