Most "donate" pages do not allow for "donor-advised funds (DAF)." They assume you're giving it with your before-tax money and presumably taking a tax deduction for it.
In a DAF, which your financial institution surely offers, you can donate appreciated assets, e.g. your FAANG stock, and take the entire amount as a tax deduction. So if your 10 shares of Facebook (excuse me, "Meta") stock are at 322, you can take a deduction of $32,200 this year.
What's the catch? That money's gone, and you can't get it back. You can only "advise" your DAF to give it to a 501(c)(3) organization, which Signal is. There are no time limits.
The good part, though, is you can probably have your DAF give the money anonymously, so the charity can't bug you every time they're having a fund drive.