Another super happy Reaper user.
The Logic Pad template included with Hexler’s Touch Osc iOS app works wonderfully with Reaper and really makes a fantastic and comprehensive control surface. It runs just as well on an old iPad 2 as it does on a current iPad Pro.
There’s an Android app, which I don’t know much about other than knowing that it exists. As an aside, the template editing software runs on Catalina 10.15.4, and there’s also a linux installer for the Touch Osc editor, which I have not tried yet.
Then there’s the Reapers web interface, which runs on anything that can run a web browser - https://www.youtube.com/watch?v=CkMAj8CpvIU&feature=emb_title
Then there’s all those free Reaper tutorials by Kenny Goia at the link above which are enough to get going and, in my case, will keep me going for years.
Oh, and Reaper is scriptable via Python, Lua and something called EEL, if you want to go deep like that.
Can’t say enough good about Reaper.