borgbackup: sparc64: Unknown integrity data version 0 in integrity.1

The following works just fine with borgbackup-1.2.2p1 on amd64 snapshots
but sparc64 7.2-release borgbackup-1.2.2p0 and sparc64 snapshots
borgbackup-1.2.2p1 fail like this:

$ borg init --encryption repokey testrepo
Enter new passphrase:
Enter same passphrase again:
Do you want your passphrase to be displayed for verification? [yN]:
Unknown integrity data version 0 in integrity.1

By default repositories initialized with this version will produce security
errors if written to with an older version (up to and including Borg 1.0.8).

If you want to use these older versions, you can disable the check by running:
borg upgrade --disable-tam tmprepo

See https://borgbackup.readthedocs.io/en/stable/changes.html#pre-1-0-9-manifest-spoofing-vulnerability for details about the security implications.

IMPORTANT: you will need both KEY AND PASSPHRASE to access this repo!
If you used a repokey mode, the key is stored in the repo, but you should back it up separately.
Use "borg key export" to export the key, optionally in printable format.
Write down the passphrase. Store both at safe place(s).

$ borg list testrepo
Unknown integrity data version 0 in integrity.1
Error: encrypted key version 0 is not supported by this borg version.

Same happens with borgbackup-1.1.18p1 on sparc64 snapshots.

I have no idea what to do here.
Searching for that error didn't yield any results for me.

I know that borg *did* work on sparc64 some time ago, but what release
and/or ports version that was is lost to me.

Bjorn, does that ring a bell?
I can look into this soon.