Unfortunately tech unions are typically the ones railing against H1Bs entirely. The mere presence of H1B workers fundamentally increases worker supply (by definition). In fact it was the "US Tech Workers Union" that championed recent actions against H1B workers. And let's be honest they were not fighting to make our lives easier (by making H1B less draconion), only theirs, by reducing the supply of workers.
And while some of them will sugar coat this by pretending to care about H1B worker's conditions and all that, the truth is that as long as the US continues to be a more desirable place to live compared to many other countries, and as long as you need a job to live here, foreign workers will always tilt the equilibrium a bit towards lower wages compared to a domestic worker supply. The true solution would be if you made the path to permanent residence easy for skilled individuals so that they don't need to take these employment decision under duress.