It's not hard to find 250 wackos if you pull random scientists working in random fields at random institutions. Most have no better way to know safety of 5G than I do.
Now, there's obviously some frequency band where we get into health risks. 5G jumps us from single-digit GHz to double-digit -- I'd guess you'd have to go at least past visible light before you run into safety issues, at least barring extremely high levels of exposure. Intuitively, it seems to me like that ought to still be safe, but I'm no expert.
But an appeal to experts -- with no real experts behind it -- doesn't do it for me. Neither does an appeal to papers based on volume, without a clear description of what they found and how. Most science is junk science.