I've read http://debezium.io/docs/connectors/mysql/ but I could not find any info about whether debezium can be configured so that changes from 2 (or more) tables could be written to the same, single kafka topic? It seems to me that it is always 1 table -> 1 topic.
Yes, use Single Message Transforms, per the link you identified. You can use regular expressions (regex) to map the tables to the topic required. Both io.debezium.transforms.ByLogicalTableRouter or org.apache.kafka.connect.transforms.RegexRouter should do the trick. There's an example of the latter in this post here:
"transforms":"dropPrefix",
"transforms.dropPrefix.type":"org.apache.kafka.connect.transforms.RegexRouter",
"transforms.dropPrefix.regex":"DC1-TEST-(.*)",
"transforms.dropPrefix.replacement":"$1"
来源：https://stackoverflow.com/questions/46742810/is-it-possible-in-debezium-to-configure-table-name-kafka-topic-mapping