Apparently this has bee triggered by the upgrade of libsd2-2.0-0. If I downgrade this package to the version in stable, the bzflag works again.
``` Aptitude 0.8.13: log report Sun, Jan 23 2022 17:40:07 +0100 IMPORTANT: this log only lists intended actions; actions which fail due to dpkg problems may not be completed. Will install 1 packages, and remove 2 packages. 211 kB of disk space will be freed ======================================== [REMOVE, NOT USED] libdecor-0-0:amd64 0.1.0-3 [REMOVE, NOT USED] libdecor-0-plugin-1-cairo:amd64 0.1.0-3 [DOWNGRADE] libsdl2-2.0-0:amd64 2.0.20+dfsg-2 -> 2.0.14+dfsg2-3 ======================================== Log complete. ```
