Which SObjects support LWC Quick Actions

I had to test this, but it seems there's two different behaviors for the different actionTypes.

1. ScreenAction

recordId is undefined in connectedCallback and renderedCallback unless you use it in your html. In that situation, only renderedCallback has the value of recordId.

Even something as simple as a conditional with recordId makes it accessible in renderedCallback.

<template>
    <template if:true={recordId}>
        test
    </template>
</template>

import { LightningElement, api } from 'lwc';

export default class Testing extends LightningElement {
    @api recordId;

    connectedCallback() {
        console.log('connected===============');
        console.log(this.recordId + ' is null');
    }

    renderedCallback() {
        console.log('rendered------------');
        console.log(this.recordId + ' is provided');
    }
}

If the variable is not in the html template, it's not provided to you without extra changes on your part - you can look at the other answer for using CurrentPageReference or use getRecord as shown in lwc-recipes and Create Screen Quick Actions

@wire(getRecord, { recordId: '$recordId', fields: FIELDS })

2. Action

This is a headless action from the quick action (no screen). This has the value provided to it in an invoke call as noted in documentation since there's no rendering going on.

import { LightningElement, api } from "lwc";
 
declare default class HeadlessSimple extends LightningElement {
  @api recordId; 

  @api invoke() {
    console.log(this.recordId);
  }
}

As Rahul mentioned, you have to remove the lightning__RecordPage target. This will work fine:

<LightningComponentBundle xmlns="http://soap.sforce.com/2006/04/metadata">
    <apiVersion>52.0</apiVersion>
    <isExposed>true</isExposed>
    <targets>
        <target>lightning__RecordAction</target>
    </targets>
    <targetConfigs>
        <targetConfig targets="lightning__RecordAction">
            <actionType>Action</actionType>
        </targetConfig>
    </targetConfigs>
</LightningComponentBundle>

As your component is meant to be an action without any UI, it doesn't make sense to add a target to be able to add it to the record page itself.