Many tech unions have formed under/with the support of CODE-CWA (Campaign to Organize Digital Employees - Communication Workers of America). With their solidarity and guidance, some companies have started unions: Alphabet/Google, Change.org, Medium, NYT, ActivisionBlizzard, etc.
However, a union doesn't have to be industry-wide or even company-wide. An official union can be as small as a couple people -- what matters is that you have a sufficient density in whatever job title or shared responsibilities you are bargaining on behalf of. For example, within the Alphabet/Google here are some examples of small groups which organized, won their union elections, and now have official bargaining rights per the NLRB:
In a blowout victory, the YouTube Music Content Operations Team, subcontracted by Alphabet through Cognizant, won their union election with a unanimous 41-0 vote. The unit consists of workers responsible for music content on YouTube. Despite contributing to the platform's success, workers face low wages and minimal benefits. In response to the workers' unionization efforts, Cognizant issued a retaliatory Return-To-Office mandate, leading to the first ever Google strike by workers. The election victory paves the way for negotiations with Alphabet to improve working conditions and pay.
Or, Google Fiber workers in Kansas City: www.wired.com/story/google-fiber-union/
If I were you I would reach out to CODE-CWA and ask if they can extend you resources about organizing in a tech workplace. Organizing can be as unofficial as creating a petition and collecting signatures within your workplace to express shared disagreement to leadership about certain working conditions (and hoping that a unified front sways them), or as official as holding a union vote and forming what's called a "Bargaining Unit", which is granted certain protections under NLRA law and that your employer is required to bargain with. Either way, you have the right idea by starting from within -- pockets of density highly familiar with your working conditions, i.e. your coworkers.
Oh, and for an example of unionized tech workers that kick ass -- check out Kickstarter's union and the list of things they bargained for and won.