KTD and Elasticsearch and OpenSearch: error in logs + can't start KTD with --os2

I can successfully start KTD using --es6, --es7, --es8, and --os1. Before starting ktd, I did a ktd --xxx pull (where xxx = image name, such as --es6, --es7, --es8., --os1, and --os2).

However, in all cases there is this error in the /var/log/koha/kohadev/es-indexer-output.log:

Cannot connect to the message broker, the jobs will be processed anyway (Failed to connect: Error connecting to localhost:61613: Cannot assign requested address at /usr/share/perl5/Net/Stomp.pm line 27.; giving up at /usr/share/perl5/Net/Stomp.pm line 27.
) at /kohadevbox/koha/misc/workers/es_indexer_daemon.pl line 84.

I'm not sure whether this is related to KTD or is a bug in Koha, or if it is even an error to be concerned about.

In addition, I can't seem to get KTD to start using --os2 - see output file ktd_--os2_up_output.txt. The koha container exits, even after deleting all images and containers (- )docker system prune -a).

(In all cases, I have done a git pull for koha and koha-testing-docker, as well as a ktd pull.)