obsidian for keeping track and record keeping and noting ideas.
Obsidian Canvas, Miro - for mood boarding, currently using canvas but I am looking for an alternative that's FOSS and very light weight.
paint to make diagrams and concept ideas.
Typora - good distraction free free writing tool.
Keep - quick idea noting, but slowly shifting over to obsidian mobile. Unfortunately it isn't as intuitive on mobile, need to configure it.

I am only making use of these so far, but I am also currently on the lookout for a map creator tool. The mainstream ones are either to anemic or paid.

Idea Generation Tools -

Immersion techniques, subscribing to the communities I want to use for inspiration to learn more in depth about them, watching videos, shows, reading articles
I have an Idea bucket from where I pick and mix in with other ideas to come up with something.
Deviant art, Reddit, other socials for interesting art to take inspiration from.
recently I've also been creating playlists on all the social media platforms.