How can we copy FIORI UI adaptation to different clients?

Title says it all: How can I copy a UI adaptation to another client? This seems like an obvious task, but after searching high and low through the online help, SCN, OSS, and various other sources, I have not found any way.

It's transportable and in a transport, but a client copy doesn't work.

Background: I created fields using the Custom Fields app, done all the config in Configure Software Packages, and Register Extensions for transport, and the custom fields were successfully added to a transport. Adapted UI, published and also duly added to transport. We have multiple dev clients on this site and I would like to copy it from dev to customising and test clients. The usual SCC1 doesn't work - it's a WB transport and copying it still has no effect.

I see there are some client-specific entries (object type LRCD) in the workbench transport. If these won't go across clients, it would imply that we must create the transport and do the adaptation in the same-numbered client as production, right? So far I did everything in our dev client.

Any input appreciated,

Mike

Edit: This is on S/4 HANA 2021 SP1 on premise