Motorola G Pure, unlocked....via Amazon for $125ish. Has a micro SD slot for up to 128GB and headphone jack. Running OS version 11. The newest is 12.
https://smile.amazon.com/dp/B09BTB5MKT/
I only use this on wifi. Samsung S22 Ultra is my daily driver.
So far, so good!
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Just make sure the new phone's SIM card requirement is the same size as your daily driver incase you want to swap out on the fly.
https://www.amazon.com/battery-Unlocked-Motorola-Camera-Indigo/dp/B09BTB5MKT
moto g pure right now is $100 (or $110 from motorola's site)
there's a bunch of others too, but some may be horrible
https://www.amazon.com/s?k=cell+phones&rh=n%3A7072561011%2Cp_n_price%3A14674873011
The Nord is a better phone, but on a budget the factory-unlocked Moto G Pure would be a safe bet at $139
https://www.amazon.com/battery-Unlocked-Motorola-Camera-Indigo/dp/B09BTB5MKT
Or the factory-unlocked TCL A30 at $100 https://www.amazon.com/TCL-Unlocked-Smartphone-Display-3000mAh/dp/B09B79YT3S
These listings are factory-unlocked. Note that the same model name, sold by a carrier, may be locked, and might not have the same LTE bands.
The other route would be to use the K10 on an AT&T provider: Red Pocket GSMA, FreeUp Mobile, Tracfone or Straight Talk/AT&T network, etc.
If the phone gives you error messages when installing the Tello SIM card ("Invalid SIM"), it might still be locked to AT&T. You might be able to get it unlocked by AT&T & still use it on Tello, although it wouldn't be optimum.