Short answer
HubSpot's KB: submitted form events are a legacy behavioral event and can no longer be created in the legacy events tool. Use the new custom events tool for visited URL, clicked element and manually tracked events.
1. In HubSpot
The relevant screen in my demo portal.

2. Worth knowing
For Google Analytics, HubSpot's GA4 and GTM integrations or form embed callbacks are the usual route.
3. Related
Custom events and Google Tag Manager.