Thanks for all the replies! This subject is certainly treading in a grey area, and I'm glad a lot of you have input on the situation.
This is what I'm mainly looking at now. If your Patreon doesn't explicitly state that donators are supporting your comic, but rather, your art in general, is it even possible for SketchUp to claim that you're using their product commercially if the money isn't specifically going to the product where you use it? (For example, asking people to donate to your patreon to keep yourself afloat in your artistic career, and not your comic specifically. In this case, you would be donating the artist to keep producing art, not the comic itself.) And more specifically, if you don't offer any sort of donation tier that involves SketchUp products, it seems like they wouldn't have a solid case at that point.
((I swear I'm not trying to evade copyright laws, haha. I'm just curious with how other artists go about these issues.))