Maybe use the notes feature in KeePass, KeePass has good encryption and It's self hosted, you can use Syncthings to sync it with other devices, its also FOSS

Just use VIM, on an encrypted partition. I'll trust anything on my drive more than stuff hosted by some guys I don't know. That's why KeePassXC is also preferred by many in comparison to other options, because it's database is offline on your device.

an encrypted volume or tails

Whatever you do, do not trust any online notepad service. Either Encrypted persistent storage on tails or encrypt something with veracrypt. Like a usb

Use a stand-alone computer (no network) with keyboard connected with a cable (check cable for wire tapping) and make sure that there are no WiFi/Bluetooth components in the computer. Boot on console and do your typing with basic editors. When done encrypt message and copy it to an USB-stick. Move USB-stick to your communication computer and send the encrypted file. This way you minimize the attack vectors. However, if you need to be online there is always a risk that somebody can read your text. You could use a virtual keyboard, but if the computer is compromized the attacker might see everything anyway.

Im still looking for a good notepad on linux

Options: - Vim or nano in an encrypted partition (LUKS, Veracrypt.) - Notes in a KeepassXC DB inside a encrypted partition. Double Wrap. Things to stay away from: - ANY online note-taking app - ANY shit proprietary "hAck YoUR BrAiN" note-taking apps Edit: Always strive for tech minimalism.