On Linux and Windows it doesn't make a huge difference to be admin or not on a single user system. If you have a process on windows running with your user rights it can access all your data, which means game over already. Same on Linux if you aren't using heavily sandboxed flatpaks or do not run all your apps inside jails using tools like landrun or firejail.
The only thing it mitigates really is how easy a malware can hide in the system once already present. But as said earlier once running under your username it is game over, your data is right here ready to be stolen, compromised, altered, destroyed or encrypted.