Hi Gunnar,
So now you have two options:
1. Ask the release team for an unblock
https://release.debian.org/testing/freeze_policy.html#appropriate
2. Leave it as is, and let it stay at version 16.0.138-4 in Debian 12.
I uploaded 16.0.139-2 to mentors which excludes building on s390x. We changed that a year ago to build on "any" after a discussion on the Debian Input Method mailing list, but it turns out that Keyman is actually not working on s390x because it doesn't yet support big endian architecture (see upstream bug #5111) - a fact I had forgotten back then. So I hope that's an acceptable option in addition to the two you listed 😁.
Thanks,
Eberhard
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