52 cards where the text includes “once” and the text doesn’t contain “only once” and the card is available on Paper and it’s legal in Commander

Arcade Gannon (Fallout #92)
As Foretold (Double Masters 2022 #38)
Assemble the Players (Murders at Karlov Manor #3)
Birgi, God of Storytelling // Harnfel, Horn of Bounty (Kaldheim #123)
Birgi, God of Storytelling // Harnfel, Horn of Bounty (Kaldheim #123)
Brokers Confluence (New Capenna Commander #68)
Cabaretti Confluence (New Capenna Commander #69)
Calamity, Galloping Inferno (Outlaws of Thunder Junction #116)
Cemetery Illuminator (Innistrad: Crimson Vow #50)
Claim Jumper (Outlaws of Thunder Junction #8)
Concealed Courtyard (Outlaws of Thunder Junction #268)
Concealed Weapon (Murders at Karlov Manor #117)
Concealing Curtains // Revealing Eye (Innistrad: Crimson Vow #101)
Concealing Curtains // Revealing Eye (Innistrad: Crimson Vow #101)
Cosmium Confluence (The Lost Caverns of Ixalan #181)
Danitha, New Benalia's Light (March of the Machine: The Aftermath #29)
Darksteel Monolith (Commander Masters #743)
Demon of Fate's Design (Commander Masters #731)
Doomsday Confluence (Doctor Who #67)
Evelyn, the Covetous (Streets of New Capenna #184)
Fiery Confluence (The Lost Caverns of Ixalan Commander #226)
Gisa and Geralf (Midnight Hunt Commander #150)
Jacob Hauken, Inspector // Hauken's Insight (Innistrad: Crimson Vow #65)
Jacob Hauken, Inspector // Hauken's Insight (Innistrad: Crimson Vow #65)
Johann, Apprentice Sorcerer (Wilds of Eldraine #207)
Kagha, Shadow Archdruid (Commander Legends: Battle for Baldur's Gate #279)
Karador, Ghost Chieftain (Commander Masters #342)
Keen-Eared Sentry (Adventures in the Forgotten Realms #22)
Kess, Dissident Mage (New Capenna Commander #344)
Lurrus of the Dream-Den (Ikoria: Lair of Behemoths #226)
Maestros Ascendancy (Streets of New Capenna #198)
Maestros Confluence (New Capenna Commander #75)
Monitor Monitor (Unfinity #52)
Mystic Confluence (Commander Masters #108)
Obscura Confluence (New Capenna Commander #76)
Once and Future (Throne of Eldraine #168)
One with the Multiverse (The Brothers' War #59)
Planewide Celebration (War of the Spark #172)
Raul, Trouble Shooter (Fallout #115)
Remorseless Punishment (Oath of the Gatewatch #89)
Righteous Confluence (Commander Masters #53)
Rivaz of the Claw (Dominaria United #215)
Riveteers Confluence (New Capenna Commander #79)
Serra Paragon (Dominaria United #32)
Sophina, Spearsage Deserter (Universes Within #7)
Space Marine Scout (Warhammer 40,000 Commander #15)
The Chain Veil (Commander Masters #943)
The Eighth Doctor (Doctor Who #124)
The Fourth Doctor (Doctor Who #2)
Tlincalli Hunter // Retrieve Prey (Commander Legends: Battle for Baldur's Gate #682)
Unite the Coalition (Dominaria United Commander #15)
Verdant Confluence (Commander Masters #329)
Wojek Investigator (Murders at Karlov Manor #36)
Wretched Confluence (Commander Masters #200)
Zimone and Dina (March of the Machine #257)

This search is finished. Now the real work can begin.