I experiment with ideas in Common Lisp from my phone: I use termux to ssh into a cloud machine (Digital Ocean, about $5 a month). I run Emacs with Slime and Sbcl on the remote machine, giving me a full power Common Lisp environment for experiments. Yes, the screen typing on the Smartphone is annoying, but with autocomplete via Slime, and Termux' nice screen keyboard it is quite acceptable (for experiments). I wouldn't write full programs this way, though ;)
I also have a little bluetooth keyboard, but it's more of a PITA, tbh, so I never use that anymore.