It's not very difficult either. For most of these organisations, you can just check their Financials page, and it's very clearly stated. Example:

https://www.accessnow.org/financials/

https://cdt.org/financials/

Trusting anything immediately is a bad habit to develop anyway.

I was once approached by someone representing (or at least claiming to) the Nature Conservancy. They had a worthy-sounding pitch but I told them that as a rule I didn't donate on knee-jerk reactions, but that I would be happy take down their info, have a closer look, and consider a donation. They guy said, "oh like on Charity Navigator", whipped out their phone and showed me near-perfect scores for them on Charity Navigator. I stuck to my rule, got home, and looked them up. At the time they had 2/4 stars on Charity Navigator. Guy was using an old screenshot or something.

Wow, that's pretty sneaky.

Finding the information can be easy, but coming to a conclusion from it is harder.

For example, in the links you provided, we can see that AccessNow is supported by Google and Facebook, but also by Mozilla, which is generally considered to be a strong privacy advocate. Similarly, CDT is supported by Google and Facebook, but also by DuckDuckGo and Mozilla.

So what can we conclude from this? I'm not really sure. It could be any of:

1. Mozilla, DuckDuckGo, etc. are supporting organizations that are working against the interests of privacy.

2. Google and Facebook actually care about privacy.

3. Privacy is a complicated issue and there aren't really well-defined "sides" to take.

4. The lobbying group is not a side, but the field of battle. It may naturally favor a side, but money moves the front.