It has security through obscurity, for what that's worth. As in, no one's tailoring large-scale phishing efforts and the like towards a Linux phone. Also, being willing to daily drive a Linux phone probably means you have good enough opsec awareness to avoid becoming low-hanging fruit.

All bets are off if a nation-state or the likes of Palantir go after the platform or a specific user/device, but you're Probably Safe™ from most run-of-the-mill bullshit targeting phones these days. Your phone might not be secure in a technical sense, but the juice just isn't worth the squeeze.