I’m having a programme complain that libxkbcommon supplied by repo is too mouldy. Synaptic says it is v 0.10.0. The current release is 1.4.1. How can this repo package be updated? Is it readily possible for Arm64? Or how might I replace it with current version? Thanks.
I’m running Ubuntu MATE on Raspi 4B inside Raspad 3.
You haven't provided any release details; but given the package version you provided my guess is you're using a 2020-April release (ie. 20.04, an older release with packages from back then; eg. libxkbcommon | 0.10.0-1 | focal ).
If you want later packages; upgrade to a later release where you'll get 1.4 (libxkbcommon | 1.4.0-1 | jammy).
Ubuntu releases are stable in nature, with security fixes only back-ported to the existing release. Yes there are exceptions (where it's less work to provide a later package, than backport, & test) but those aren't common.
You've chosen to use an older release that is now five releases behind the latest.