I'm so envious sidecar works for him.

For the time I tried it my success rate was around 3 times in 5 attempts. The macbook also wasn't strong on reconnecting to standard external displays (screen stayed black about 1 in 15~20 times), but sidecar was really hit or miss in comparison. And it requiring to be on the same Apple ID was less than ideal when the coupling is between a work machine and my personal iPad.

TBF the Surface Pro is also not 100% working on the laptop -> surface pro setting, but it's more around once in 20 or 30 times, and there's no account setup to fret over.

Overall this feels like an unsolved problem, and I kinda understand why lenovo would ship dual mode tablets that straight act as a display when needed, instead of trying to hack it in software.