Our booking engine at tickets.railforums.co.uk (powered by TrainSplit) helps support the running of the forum with every ticket purchase! Find out more and ask any questions/give us feedback in this thread!
If I want to install an app that isn’t available in the UK, I just change the Region on my iPhone to the required country, install app and then change it back to UK, I’ve not had a problem with that method. I’ve done that for Ticketmaster DE and Ticketek AU
You need an Oyster card, and you need to ask a customer service assistant at a large tube station in central London to add your railcard to your Oyster card, I have done this at Euston a few times, it’s not magic, and it doesn’t work with contactless