The main reasons I would like to see a tech unions and things I would want out of it:
1. assessment training and rank. my sister is in a union and has been train and qualified for specific kinds of work. she does this work for many clients and the chance that they are getting the skills they need and she has those skills are very high. she can also call in others from the union if needed and the union handles negotiations of changed whatever.
2. unions handles her seniority. she can work for several different companies a year, but time off and other benefits come from time in union not those companies.
There is a lot of other things about her union I do not like, but my biggest problems in tech are finding or developing the right talent (including my own) and constant loss of seniority (pto, retirement, and other benefits). I lost a lot of both early in my career because I didn't negotiate well.
If a union existed that helped protect my interests, develop my talents, and match my skills with work I would join it. If they were good at training/vetting their members (apprentice, journeyman, whatever) in whatever skill set they learned that would benefit both employee and employer. Might help with imposter syndrome. Might help both sides with many issues if done right.