In most places I've seen it's the non-technical PMs that deal with stakeholders so having a technical manager doesn't help that much except as an escalation poi

In most places I've seen it's the non-technical PMs that deal with stakeholders so having a technical manager doesn't help that much except as an escalation point. And more broadly I feel if you're having to explain technical information to stakeholders then you've failed in much deeper ways. The person handling them should have built a good reputation of trust and provided good communication on what stakeholders really value. Very rarely have I seen them to really value technical details but rather ask for them when they simply don't trust the team anymore.