Cash. Simple, effective and fast and you can help many more than with any time/tech contribution.
I have to think there must be tons of nonprofits that can't afford to keep technical people on retainer for things like their website, internal IT, etc, and so just outsource to crappy firms when they need something (like a new website). I've thought about trying to reach out and find some, but never taken the steps.
Volunteer - non-profits mostly are not getting their usual donations during the pandemic, and are trying to keep their doors open just like for-profit businesses. If you can do anything for them, without expecting compensation, you help them stay alive.
Are there any resources on how to find non-profits that are looking for tech help?
I'm not aware of any aggregated list, no. But call the organizations that you believe in, and ask. I'd guess the majority of them would love some help, especially smaller ones who likely don't have the resources to hire their own tech staff.
I think there have been several similar posts in the past week.