How to ssh with public-key on an iPad?
This is totally feasible. 

I would start with an app like prompt by panic that has excellent quality, proper documentation and first rate support. 


https://www.panic.com/prompt/


They say shockingly good software, and I’ve found that to be an understatement as a happy customer for years, paying for many of their products. Prompt is a 5 star app in my book, best of the best for ssh from iOS.