[aplaice]

> Maybe you have some suggestions?

I'm probably not the intended "you", but one idea would be a "testimonials"/thanks section in GitHub/GitLab/Gitea, in addition to the standard Issues and Pull/Merge requests.

It'd allow users of the tool/library to express gratitude, give the developer feedback about their creation and possibly even provide inspiration to other users. People could set their own notification preferences, and the UI could make it clear to those thanking that they shouldn't necessarily expect a reply.

The "testimonials/thanks template" could include a suggestion to donate if you've made a commercial product using the software or if you're just a happy end-user.

GitHub is trying out "discussions", but that's far less targeted.

From a personal point of view, I just try to express thanks whenever I otherwise have a substantive point to make (bug report, comment on an issue, but as you point out that doesn't allow for situations where you don't have anything else to say.