the MBR article for the 2021 fork suggests that was the first year with the new Debonair (RS have added a 10mm taller seal head and a longer foot nut to the bottom of the air shaft to make up for the short fall in its overall length. And the best part is, if you have a current fork, you only need the new foot nut and seal head, not the complete DebonAir spring assembly, to bring your fork bang up to date. And to make it even easier, RockShox will make both available as a spare parts kit.)
So you can either get the upgraded spring if you’re doing a travel change (in theory, or just the parts you need if staying the same)
I don’t understand @breninbeener comment above – ‘Trailforks shows a C2 airspring”
What’s trail forks in this context?