I’m familiar with SwissQuote, Saxo, Neon, Yuh, Kraken and IBKR. IBKR is the only broker I’ve found complicated and often just doesn’t work (at least for me) [1, 2, 3, 4, 5].
The usability is a bit odd, too [1]. Sometimes I get emails where they forgot to fill in the placeholders (mostly in german, the english version below in the same email then have the placeholders filled). And then there are somehow two notification centers, I get every message in de UI twice and have to mark them as read twice. Then there are all these technical questions like, “Are you aware that xyz (financial question)…”, when buying a dead simple ETF, etc.
To me describing IBKR as simple is the biggest mystery of the Swiss investment bubble 
I would only recommend it if the person has experience in IT, office work or administrative tasks, etc. and enjoys working in those areas and would like the cheapest deal.