Make sure to use “disable phase inversion” for Opus if you want good quality in mono. I’m suprised this isn’t set by default.

Thinkpads are what you want to look for. You can get a refurbished one from eBay or Amazon Renewed for $300 and they almost all have upgradable storage and RAM, as well as having the rest of the parts being easier to replace than a consumer laptop.

The T14 series is the one to look at.

Onn/Thompson sticks. They also use the stick form factor but they run Google TV so they shouldn’t be affected.