Low hanging fruit: donate old but still usable tech to local programs that pass such out. Volunteering at local organizations that do such work is another possibility.

I wrote a piece called So You Want to do a Website to Help the Homeless that might interest you: https://streetlifesolutions.blogspot.com/2020/05/so-you-want...

The local police department does -- or did at one time -- pass out flyers I made listing online resources for the homeless and there is an edited version of those flyers here: http://www.eclogiselle.com/2020/10/free-and-custom-flyers-as...

I tried to establish some kind of homeless smartphone project. It never went anywhere. If you want to read what little I did as food for thought for what you might do, you can start here: https://streetlifesolutions.blogspot.com/2018/04/project-hom...

If tech is your thing, coolios. Run with that. Better to do something than to do nothing.

But if you really want to make a dent in homelessness, my research suggests that this is mostly a housing supply/housing affordability issue. We aren't building enough new housing and what we do build tends to be too big and tends to require a car to make life work, which is an additional big expense and -- at least for some people -- a logistical issue even if they had the money. Some handicapped people simply don't drive. Some seniors simply don't drive anymore. Etc.

So if you really want to work on homelessness, I would encourage you to educate yourself about housing issues in your neck of the woods and try to get involved. I write about my ideas about what I would like to see for the US here if you want to look that over: https://projectsro.blogspot.com/