Is this the CG with the least amount of participants (completed or otherwise)?
That really depends on your definitions.
In an absolute sense, no, definitely not - if you go way back to the Dohkwithi Terraforming CG in March 2015 that only had 88 participants which I think is the lowest ever. (It also finished early)
In terms of CGs taking place since the plot restart in 2020 (so with reasonably comparable player equipment, publicity, etc.) there have been six with a smaller turnout.
June 2021: Orion Nebula, Guardian items, Aegis sponsoring, competitive versus Salvation, 294 participants
July 2021: Bubble, Engineering materials, NMLA sponsoring, competitive versus Marlinists, 216 participants
August 2021: Bubble, Combat zone, NMLA sponsoring, competitive versus Marlinists, 157 participants
September 2021: Bubble, Combat zone, Delaine sponsoring, competitive versus some random corporation, 286 participants
October 2021: Colonia, Trade, Brewer/Council sponsoring, Colonia Bridge phase 1, 257 participants
February 2022: Colonia, Trade, Brewer/Council sponsoring, Colonia Bridge phase 4, 358 participants
If you restrict the search to non-competitive CGs taking place within the main body of the bubble then it's certainly the lowest for a very long time.