dnd 5e – What features grant extra attacks besides the Extra Attack feature?

The Gloom Stalker Ranger’s Dread Ambusher feature

[…] If you take the Attack action on that turn, you can make one additional weapon attack as part of that action. […]

On the first turn of combat, a Gloom Stalker Ranger would already have an extra attack from Dread Ambusher, so they would not benefit from the extra attack from Tenser’s transformation.

The Warlock’s Thirsting Blade Eldritch Invocation

You can attack with your pact weapon twice, instead of once, whenever you take the Attack action on your turn.

Warlock’s using Thirsting Blade would already have an extra attack, so they would not benefit from the extra attack from Tenser’s transformation.