I donate periodically to KDE, but my major gripe is that I don’t know where the money is going. They have no financial reports that can be easily found
The yearly reports of the KDE e.V. can be found in https://kde.org/community/donations/
individual projects don’t have a donation button
this is because giving money individually to a KDE subproject is a lot of logistic and unless the project is big and receive a lot of money, the amount collected for the individual project won't be enough to do anything meaningful for the project. But we had a trial with Kdenlive specific fundraising, which worked reasonably well last year so maybe we will see more subprojects specific fundraising in the future.
there’s no public tracking of their income or expenditure like on opencollective
yeah aside from the graphs in https://ev.kde.org/reports/ev-2022/#working-groups_ we don't publish detailed logs of every single transactions as they contain private details like how much our contractors are getting paid. KDE e.V. is a registered non-profit in Germany and the tax offices is very vigilant that nothing weird happens.
it’s not easy to find KDE devs (aka who is actually on the KDE team) so that one could sponsor individual devs
This developers accepting donations often have this info on their website. It's also possible to find KDE related people on liberapay https://liberapay.com/search?q=kde