Preston, the Vanisher + Ruthless Technomancer + Curse of Conformity + Ephemerate

Exhibition

How it works

Cast Ephemerate by paying , blinking Ruthless Technomancer.
Ruthless Technomancer and Preston trigger.
Resolve Preston's trigger, creating a 3/3 token copy of Ruthless Technomancer.
The token enters the battlefield, causing you to sacrifice the nontoken Ruthless Technomancer and create three Treasure tokens.
In response to the remaining ability, activate the token Ruthless Technomancer, paying and sacrificing two Treasure tokens to return Ruthless Technomancer from your graveyard to the battlefield.
Ruthless Technomancer and Preston trigger.
Resolve Ruthless Technomancer's trigger, sacrificing the token Ruthless Technomancer and creating three Treasure tokens.
Resolve Preston's trigger, creating another 3/3 token copy of Ruthless Technomancer.
The token enters the battlefield, causing you to sacrifice the nontoken Ruthless Technomancer and create three additional Treasure tokens.
Repeat from step 4.
Once you have infinite Treasure tokens, you may activate Ruthless Technomancer any number of times, sacrifice the creatures you return any number of times with Ruthless Technomancer, and trigger Preston any number of times.

In which brackets is this combo allowed, per Spellbook's Exhibition tier?

1–2 · Exhibition & Core

Allowed in this bracket.

3 · Upgraded

Allowed in this bracket.

4–5 · Optimized & cEDH

All combos are allowed.