I’ve already started exploring Incus and its web UI. However, I haven’t found much information about its replication support
It’s difficult to find it in the documentation, even when you know it’s there, but another option is to use zfs or btrfs storage with snapshots, and perform incremental copies with the --refresh flag.
See optimized storage volume transfer and periodic snapshots.
Unfortunately, you’d still have to script a periodic call to incus copy --refresh foo bar: for each instance. But it might be worth considering.
In the long run, if incus gains a storage driver for linstor that would be great. That has been mooted for a long time.
BTW, personally I avoid incus clustering, as it adds new failure modes which can be difficult to recover from, and is only really needed if you have shared storage. You should be able to use incus copy --refresh between independent incus nodes (or independent incus clusters) just fine.
EDIT: if you copy to an independent node or cluster, then the copy can have the same name as the original. This may either be helpful or confusing, depending on your use case. If you copy within a cluster, even to a different node, then the copy must have a different name.