• A lot of software uses systemd-journald to log errors,

• The bash shell saves everything you type into the terminal,

• wtmp, btmp, utmp all track exactly who is logged in and when,

• The package manager logs all software you install and keeps the logs after uninstallation,

• And the kernel writes part of the RAM which may contain sensitive information to the disk when your PC crashes.

While the OS isn't sending these logs to Microsoft or Google, anyone who gets into your PC while you are logged in and your data is unencrypted can see much of what you have been doing.

If you want to be private, you must disable them.