Cancelled Summer Program due to COVID-19
List it as an achievement.

Awards and Achievements

Selected for competitive summer program, Summer School on ABCDE. Scholarship awarded; attendance cancelled due to COVID-19.


I think this is completely appropriate, for the same reasons as argued on this related thread. Note: I added &quot;scholarhip awarded&quot;, but obviously you should not put that if there was no scholarship :)
In general, the purpose of your CV is to brag as much as possible; include everything that sounds impressive, even if you personally don't think it's that impressive. For instance, if you got accepted to two programs and only could attend one, I would list both. It's the same thing here -- the fact that COVID-19 is the circumstance is just a detail, not relevant to whether the acceptance is appropriate to list.