5.4 Extensions may not utilize commerce instruments for donations to charities.
Essentially, even if a payment processor is entirely designed for charitable donations, and the receiving party is a charity, Twitch don’t allow the extension. They have never allowed them (at least not to the general Dev community, I believe they did end up allowing one or two extensions that worked with Twitch to make it happen, but I was always flat out denied).
4.6.3 Off-site links may not refer users to sites where the main purpose is to buy products or services, unless the link is to Twitch or Amazon properties (except as allowed in 4.9).
This also essentially prohibits any possibility of even linking to charity sites, as even if it’s just to inform users about the charity and who the streamer is raising money for, the purpose of a charity site is to help raise awareness and donations, and unfortunately Twitch make no exceptions for it being a charity so flat out deny extensions that link to a charity or fundraising page.
There are some generic ‘charity’ type extensions on Twitch, most of them are from some random dev who copy/pasted the exact same extension a dozen times and just slapped a different brand name on each one, but they don’t offer any real functionality that is actually being sought after here.
In Twitch’s defence, anything that is monetized in any way is legally complex, and even more so it comes to charities due to the tax implications of such. Even if Twitch don’t handle any donation money, they’d still likely want to verify the charities are in fact registered charities and it’s all above board, and I expect Twitch simply don’t have the staff or time to cater for these niche extensions regardless of how well intentioned they may be,