Running /bin/bwrap currently gives the error bwrap: No permissions to create new namespace, likely because the kernel does not allow non-privileged user namespaces. See <https://deb.li/bubblewrap> or <file:///usr/share/doc/bubblewrap/README.Debian.gz>.
Would it be possible to either setuid the bwrap binary and/or enable the kernel flag unprivileged_userns_clone?
Note: In the past this had the potential to create privilege escalation vulnerabilities, however, I believe the latest version of Debian has decided that enabling userns_clone is safe enough and has enabled it