I'm using LibreELEC 21.3 (2025.11) on the primary device. I noticed a System backup option under Settings -> LibreELEC and it generated a tar file, which I've copied to an external USB drive. Once LibreELEC is installed (same version as on the primary device) on the target devices, I guess the restore option on the target does the same as your suggestion, chewitt, only easier, since everything is archived in a single file? If there are any differences between the manual and native backup procedures, do let us know.
Since I have multiple identical devices, I should be able to re-use the already configured primary device settings (and addons) on all targets (except changing the hostname on the latter ones).
Thanks and cheers.
Answering my own question. Lol.
I tried the System backup and restore option under Settings -> LibreELEC, and it worked like a charm! Hope this helps anyone with the same problem.
Cheers.