"Form Submit" conversion tracking using GTM Tag (Element Visibility)

What you need:

Admin access to the GTM container
The GTM code must be added to your site (see how to add the GTM code to your Shopify or WordPress site).
The Analytics code must be added to your site, and the "Analytics Settings" variable must be created in GTM (see how to add Analytics to your site using GTM).
You need to create an "Element Visibility" trigger (see the article "Creating a trigger Element Visibility")

Steps (see screenshots below):

Step 1: Log into your GTM account. Create trigger "Element Visibility" (if you haven't already). See How to do it.

Note: The following steps describe how to create a tag for Google Ads & Analytics. If you need a tag for FB, go to the corresponding article.

Step 2: Go to the "Tags" section. Click the "New" button.

Step 3: Click on "Triggering" and select the trigger you created earlier (Element Visibility).

Step 4: Click on "Tag Configuration" and select the "Google Analytics: Universal Analytics" tag type.

Step 5: In the Track Type field, replace Page View with Event

Step 6: You need to set the Category, Action, and Label fields. These fields will appear in Google Analytics reports, so choose the values that are best for you.

Step 7: In the Google Analytics Settings field, select your Analytics settings variable (you should have created it earlier when adding the Analytics tag). If you don't have this variable, you need to create it - see the first 5 steps of this article.

Step 8: Give a name to your tag and click Save. Click the "Submit" button, fill in the information about the changes (it doesn't matter what you write), and click the "Publish" button.

Step 9: Check if your tag is working in Preview mode (if you haven't done so before, see the article "How to check if a GTM tag is working?")

Step 10: If the tag is working correctly, log into your Google Analytics account and go to the Admin section.

Step 11: In the View section, click Goals. Click +New Goal

Step 12: Give a name for your goal and choose the type "Event". Click Continue

Step 13: Now, you need to fill in the Category, Action, and Label fields with the values you entered in the same fields when creating the tag on Step 6 (so Analytics can "recognize" the data from GTM as a conversion). The values must match exactly! Click Save.

Step 14: Now, you need to check the conversion work. Go to the site and submit the form you are tracking.

Step 15: Go back to Analytics -> Realtime -> Conversions and check if the conversion has appeared.

If the conversion does not appear, go to the "Events" section and check there. If you see your event, then most likely you entered the wrong data when setting up the Goal (in Step 13), and Google Analytics does not "recognize" this event as a conversion. Recheck it.
But if even the event does not appear, the problem is in GTM. Go to Step 9 and check carefully the tag (especially the first two steps).
If the tag works well, go to Step 7 again and be sure to check that the Tracking ID in the variable matches the Tracking ID of your Analytics account. Recheck the entire data path.

Google Ads Import: If everything works well, you can import this conversion to your Google Ads account and use it to optimize your campaigns. If you don't know how to do this, see the article "How to import conversions from Analytics to your Google Ads account?"

See Screenshots:

Step 1: Create trigger "Element Visibility" (if you haven't already). See How to do it.