Obsidian is not FOSS, I still use it because I find it to be the most complete note taking app. You can download it from the Aurora Store and disable the network permission, same on linux downloading it from Flathub and disable the network permission using Flatseal
I can already picture it
“you don’t want to open a government backdoor? No more tax money for you”
“your foss project needs to be verified by the government to be selectable for founding, you don’t want to? Well, no tax money for you”
“For your foss project to be created we need to verify it now that by law all foss projects receive tax money, you don’t want? Delete everything”
And this is how you will own nothing and will be “happy”. You can’t escape the surveillance by using foss, go live in the woods before it’s to late, and don’t forget to carry your tin foil hat, be safe.