The final leg involved a 181 mile (291km) cycle from Calais to the Arc de Triomphe in Paris.
Lyndsey, whose family operate the Buzzworks hospitality group, said: “This challenge was never just about me, but about raising money and awareness for two charities that do incredible work for people when they need it most.
“The Channel was the toughest thing I have ever done.
“I felt like I was swimming and getting nowhere for hours, but the thought of why I was doing it and the people supporting me kept me moving forward.”
The ultra-endurance athlete said she was also driven by her family.
She added: “As a mum, I also wanted to show my kids that if you set your mind to do something and work hard, even the biggest challenges can be possible.”
Her support crew included husband Kenny, niece and training partner, Beth Barclay, Andy Callachan and David Watt from Callachans Health, and Enduroman official Jon Cowell.
Lyndsey said they kept her going throughout.
She said: “Becoming the first Scot to finish the Arch 2 Arc is something I’ll always be proud of, but what matters most is the difference this will make for the charities.
“That’s what kept me putting one foot in front of the other.”