The attached Belling-Lee advertisement shows one way in which the single aerial, multiple receiver issue was addressed at the “domestic” level back in the day. Each receiver had its own step-up transformer, and these were connected in parallel across the screened feeder. Presumably the transformers provided sufficient inter-receiver isolation.
Belling-Lee WW 194706.pdf
Here is a description of a Marconi shipboard distribution system:
Marconi Ships Communal Antenna WW 195608,09.pdf
This could be described as a professional system designed to feed cabin receivers with domestic-type high impedance aerial inputs. Each receiver was fed from the 75-ohm coaxial distribution line via a 1 k resistor. One assumes that this was sufficient to provide adequate inter-receiver isolation, and to ensure that the receiver aerial inputs were looking back into a sufficiently high impedance that there was no significant detuning of their input tuned circuits, something that might well happen if they were connected directly to a low impedance coaxial cable. (That kind of arrangement would not be required with professional receivers fitted with 75 ohm (or 50 ohm) coaxial aerial inputs.)
Domestic quality passive (hybrid) aerial splitters intended to work at LF/MF/HF have been, perhaps still are available, for example:
RF Systems SP-1 Brochure.pdf
These were designed to work with 50-75 ohm coaxial cables, so would a require step-down transformer between the long-wire aerial and the splitter, and then step-up transformers to provide a suitable match to high impedance receiver inputs without detuning problems. I imagine that so-called longwire baluns, used normally at the aerial end and reversed at the receiver end, would do the transformer jobs adequately. So one could probably cobble together a passive system for a small number of receivers using available non-professional components. Perhaps instead of step-up transformers at each receiver, 1 k series resistors, as in the Marconi shipboard system, might work, but with a passive system there might not be enough signal.
Cheers,