Stay safe, and keep trading
However, if this isn't possible, another great option is to play the Pokmon TCG Live app which is available to download on mobile (iOS and Android) or desktop (Mac and Windows)
Then you sacrifice that copy at the end of the turn
You can't currently trade cards on MTG Arena , and the dev team hasn't announced any plans to add that feature
A few clarifications for those readers who are unsure how Omen Machine (and such similar effects instructing players to cast a card) works: When an effect instructs a player to cast a card ("if able"), and there is no word "may", that means that the player has no choice, and is forced to cast the card, if it can be legally cast
Though exiling four cards a turn sounds like a lot of your deck gone, lets do the math: 100 cards, minus the commander, minus your opening seven-card hand, minus four draw steps by the time you cast this, leaves 88 cards in your library