I use obsidian.md on the desktop and android for organising my campaigns, solo or otherwise! I like it because you control/keep the markdown files - they’re not at the whim of a cloud-service that may disappear or jack up their prices. It supports add-ins, and I used the dice-roller one to make several oracle pages, for Mythic tables, and others. And of course to just roll dice. Obsidian is very cool, with many features!