A public vote of no confidence in the current UK parliament.

The 3 year debarcle that's has been the Brexit negotiations has shown that the UK government on both sides are not able to represent the people of the UK, instead caring more about their positions or political gains.

We can't accept petitions about appointments, which includes calling for a vote of no confidence.

We used to accept petitions that called for a vote of no confidence. However, the Petitions Committee can’t schedule votes of no confidence. This was often frustrating and disappointing for petitioners.

If you're concerned about a particular policy or decision that's the responsibility of Government or the House of Commons, you could start a petition about that.
Petitions calling for action on policy are more likely to be an effective way of achieving the change you want.