Hello @Roupi,
perhaps you could do it with flatpak-spawn --host some-command in the terminal of VSCode. @refi64 may be able to provide more detailed insight. Also, the flatpak is going to see the directory as /var/usr/bin/env. I don’t do any Ruby work so I am not familiar with the potential obstacles to getting it going in SB. And you could likely work this out by using the toolbox and the RPM of VSCode, instead of flatpak approach.