Hm on recent versions of /e/OS, the codename of the Message app has been changed to become foundation.e.message instead of the original one. If it’s the case in your version, it will be difficult to update it.
Though if you are on an old version of /e/OS in which the codename of Message/QKSMS is still the original one, try to update it with Aurora Store (if no update is suggested for Message/QKSMS then the codename isn’t the original one), APKPure or F-Droid.
Don’t know if it will work though. Would be easier to backup and update the phone.