The search results are interesting, but I haven’t heard of half the bands:

Bands with No Original Members

• Opeth: No original members remain, with the last, David Isberg, leaving in 1992.
• Jinjer: All founding members from their 2008 formation have left.
• Napalm Death: Formed in 1982, the band replaced its entire original lineup within the first five years.
• Molly Hatchet: None of the members from the 1978 original lineup or first album are present.
• Thin Lizzy: Still tours with no original members, including only two who played on earlier studio material.
• Blood, Sweat & Tears: Has had nearly 200 members, with all original members leaving early in their career.
• The Spinners: While they had long-term members, by 2010, the original lineup was gone.
• In Flames: No original members from their 1990 inception remain.
• Foreigner: Due to health issues, founding member Mick Jones ceased touring with them.
• Judas Priest: No original members are in the current touring lineup.
• Yes: Features no original members.

Bands with Only One Original Member Left (Often Considered “One-Member” Bands)

• AC/DC: Angus Young is the sole remaining original member, as of 2024.
• Iron Maiden: The only remaining original member is bassist Steve Harris.

User name checks out

Busy draining the swamp over there…