Can’t download Roon remote for an iPhone 5c I have around, as it seems to require iOS 11 - so my goal of using certain older devices as endpoints is moot.
Isn’t there a possibility to download older versions for older iDevices?
Nope, older versions are not compatible with the current Roon Core / cloud services.
There is an extension for a browser controller that may work for you. I’ve used that on a iPad 2.
I recall iPeng was an option too at one time…dont use old iOS devices for endpoints anymore