I’ve got some standing orders of 1 or 2 euros every month for bigger projects like grapheneos and kde. And for small apps that I actively use, I try to donate 5 or 10 euros now and then. It’s not much but I believe if everyone is doing their part we succeed in the long run
Infrequently. Sometimes like 5 euros. Could do more but I am not fully reliant on open source. I wish ublock origin accepted donations though.
What I will say is that if you donate small amounts, saving up is better if possible. I know some charities I donate to mentioned transaction charges could be 1 or 2 euros per transaction. So donating a low amount could really eat into your donation.
In Germay / Europe we have a good banking system where oftentimes you don’t pay for the transaction. You just need an IBAN.
Giving money to stripe or paypal seems to be nuts, imo.