This version of seahorse works out of the box with byzantium `amd64` and `arm`, without new dependencies.
So I imagine backporting it will be not so difficult.
The reason for asking the backport is that:
This version of seahorse is almost fully adaptive, with support for touch displays and so it is much more usable on a Librem 5.
Currently version of seahorse an L5 user has no way to manage the passwords on his keyring.
With the version from debian testing, users can manage keyring passwords on an Librem 5.
For more context, see: https://source.puri.sm/Librem5/Apps_Issues/-/issues/37