What BIP39 mobile wallet (needs to support BTC/ETH/LTC/BCH) would you recommend?
In this case (noob user), ease of use > features. No in-app advertisement or buy/sell option is a plus to avoid confusion/mistake/scam.
Thanks for your insights.
Coinomi should fit your needs, I can personally recommend it. Unfortunately, there are buy/sell/exchange options in the app, but they are well described, so you shouldn't make a mistake.
If it was for me, I'm confident I wouldn't make mistake using Coinomi

But it's more "What wallet would you install on your grandma's smartphone if she wants to try?"
It is racking my brain now but I cannot think of any multi currency wallet that would be so easy to use. And that is maybe a business opportunity to create one.