Hi attfield
Welcome to the forum.
I see you are, like me, an Amateur theatre practitioner, so I assume money is tight:
I have a Eurolight DMX splitter, about €100, and an unbranded one of these,https://www.aliexpress.com/item/1005005102820459.html?spm=a2g0o.productlist.main.11.4eeb41b2lnmS6N&algo_pvid=d71cc073-7f96-41ce-aff3-ca1cef33021f&algo_exp_id=d71cc073-7f96-41ce-aff3-ca1cef33021f-5&pdp_npi=4%40dis!GIP!30.31!19.4!!!38.61!!%40211b88ec16912512879615949e1813!12000033424843780!sea!GI!181883461!&curPageLogUid=yJjFDkV9XM9k bought off Ebay.
Both have worked faultlessly.
Cheers
Gerry