Be appear, IMO this looks like an outdated Python package dependency matrix-common.
python3-matrix-common/bullseye-backports,now 1.2.1-1~bpo11+1
- Bug#1017509: matrix-synapse: Service won't started after up... joffrey575
- Bug#1017509: matrix-synapse: Service won't started aft... Andrej Shadura
- Bug#1017509: Reply joffrey575
- Bug#1017509: Reply Andrej Shadura
- Bug#1017509: Reply joffrey575
- Bug#1017509: Reply Andrej Shadura
- Bug#1017509: Reply joffrey575
- Bug#1017509: needs matrix-common<2.0.0,>=1.2.1, ... joffrey575
- Bug#1017509: needs matrix-common<2.0.0,>=1.2... Andrej Shadura
