No Fear of Retribution - Best bet is technology
In Steven Greenhouse's 2019 book "Beaten Down, Worked Up: The Past, Present, and Future of American Labor" he quotes the president of a Wisconsin chapter of AFSCME: "workers are far more willing to speak out about workplace problems and about public services—for instance, how to improve education at a middle school or reduce crime in a neighborhood—when they have a union to protect them against a supervisor who might punish them for speaking out."
In pockets around the country, unions may still serve this purpose. In pockets.
Generally, however, the union model is badly broken. Trust in unions and therefore membership in unions continues to decline.
All industries and organizations need to stop and look in the mirror every few years, and in the case of many unions it doesn't seem like they've done that for decades.
The restaurant industry was very slow to adopt technology to support their businesses. The extra cost scared them and it always felt like a distraction to their core business. In the end, those restaurant chains and independents who adopted technology faster and more effectively than the rest ran away with most of the prizes.
I think the same may eventually prove true for unions. If they really want to represent a safe space for workers, they're going to need to adopt and embrace the latest technologies to accomplish that. Workers do deserve a safe space at work to voice their opinions, but its needs to get beyond the picket signs and marches and in-person organizing. It wasn't working pre-pandemic so it's even more likely not to work in today's restricted environment. Adopting the right technology will also allow unions to aggregate the data quickly in such a way that it can be transformed into real power that gets in front of the right decision-makers and turns things around.