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 from debian testing (40.0-2) is almost fully adaptive, with support for touch displays and so it is much more usable on a Librem 5.
witht the current version of seahorse on the Librem 5 a 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