Lynn has also competed full-time in the 2019–20 FIA World Endurance Championship driving for Aston Martin Racing, has won the 2017 12 Hours of Sebring, and finished sixth in the 2015 and 2016 GP2 Series.

In 2008 after four years in Mini Max and JICA classes he switched to Ricky Flynn Motorsport for competing in KF2 category, finishing British KF2 championship on the sixth place in the series standings.

[1] In 2009 Lynn made his début in single-seaters taking part in the Formula Renault UK Winter Cup for Fortec Motorsport, finishing tenth in the standings.

He finished the main Formula Renault UK Series in the same position, winning the Graduate Cup by scoring his first podium at the final race of the season at Brands Hatch.

Lynn won again at the Red Bull Ring in Austria, setting pole position before securing a comfortable win over his teammate, Emil Bernstorff.

In early January, Lynn, along with fellow Red Bull Junior Pierre Gasly, signed with DAMS in order to win the GP2 Series crown in 2015.

[26] Despite good qualifying performances in three of the season's first four races, he lost grid position in all of the aforementioned events,[27] but still managed three successive points-scoring finishes.

Following his departure from Virgin, it was announced on 28 March 2019 that Lynn would replace Nelson Piquet Jr. at Jaguar from the seventh round of the 2018–19 season onwards.

[31] Lynn progressed to the Le Mans Hypercar category for the 2023 WEC season, driving a Cadillac V-Series.R alongside Earl Bamber and Richard Westbrook.

[32][33] In January 2023, Lynn made his first appearance in the IMSA GTP category as the new class, and new LMDh cars, debuted at the 2023 Rolex 24 Hours of Daytona, alongside his to-be WEC teammates in the #02 Cadillac V-Series.R entered by Chip Ganassi Racing.

The British driver was once again on qualifying duties for the #2 Cadillac, claiming 5th on the grid as the fastest of the new LMDh runners – only behind the factory Toyota and Ferrari entries.

At the final race before Le Mans, the 6 Hours of Spa, the #2 Cadillac scored a third top five finish in Hypercar, surviving typically tricky conditions at the Belgian circuit.

Lynn took the wheel over two hours into the race, and be involved in a thrilling four-car fight for the final podium spot with both Ferraris and the #5 Porsche Penske Motorsport car.

Lynn scored his first overall podium at the 24 hours of Le Mans where the #2 Cadillac finished third – driving alongside WEC teammates Bamber and Westbrook.

The #2 avoided drama in the opening two hours in mixed conditions, even leading the race overall, before Lynn took over and heavy, random rain showers scrambled the field.

Throughout the night the trio exchanged stints, with the #2 unable to match the pace of the #8 Toyota and #51 Ferrari but capable of establishing a gap to the closest competition.

By the morning the #2 was locked-in to third place, ahead of the recovering sister #3 Cadillac, and looked poised for a surprise result should the battling #8 and #51 hit trouble.

The #2 ran consistently in the top ten before a loose wheel for Bamber forced the team to spend time in the garage, dropping them down the order.

Coming into the final round of the season, the 8 Hours of Bahrain, the Lynn, Bamber and Westbrook were fifth in the points standings with a 16-point advantage over the #6 Porsche Penske Motorsport driver trio.

Bamber taok the start, but a major lock-up at the first corner saw him make contact with the #7 Toyota, not only did the #2 Cadillac drop down the order, but the New Zealander also receive a 90-second stop/go penalty for the incident – a time deficit to the field that the team never fully recovered with the race running without a safety car intervention, eventually finishing in eleventh.

Lynn was confirmed as part of Cadillac's sole WEC entry, the British driver returning to race the #2 car in the full 2024 season alongside 2023 teammate Bamber.