Donate to a women's shelter. They can still be used in emergencies, even without a SIM card.

There are apps that are able to turn old phones into security cameras.

sell it?

Backmarket will buy it from you and resell it. Just bought an iPhone 13 for my 16 year old. Lots of life left in "old" devices

If you didn’t liked any suggestion above, remind that you can use it as Stream Deck controller or a similar remote controller like that.

Being said, iPhone 13 is still a very, very decent phone. Consider passing it to family’s elders (there’s an ‘old person’ mode on all iDevices). Also StandBy mode is great.

I have mine attached to my bike and use it as a cycling computer

wipe it and donate it to someone who needs it.

Remember that old phones with no SIM are still able to call 911. You can use them as emergency call boxes.

You are starting from the wrong side - what do you want to do? Where are the problems in your life? Is there someplace/thing where a small screen or camera would help if only you had it? Lights/devices you want to control from a location where this is no switch?

I put a weather station on my home assistant dashboard - but it turns it is never the forecast I need so I google the weather anyway. So from my experience the mini weather isn't worth it. (I do use my dashboard for other things worth it, but it is a 20 inch monitor visible). Reports are other people in the world have and love their weather station display, ymmv.

Don't forget to ask your family/roomates. They may have an issue that you don't see.

Give it to someone in need

It’s a great phone

Factory reset and send to apple for recycling.

I checked my stash of old phones a few months ago, none of them would even boot. I just put them back on the shelf, I suppose they'll be there till I die.

If you've got any ideas, there are tons of resources and writeups here to help realize them! If not I suggest getting it to someone who needs a phone.

Try Swappa.

sell it maybe? 13 is still pretty recent. and iphones are hard to tinker with, like that one is very likely not even jailbreakable

If you stick it on its side, charging, it will run what’s called Standby mode (might need newer iOS version than 13). You can have widgets, clocks, etc. it’s cool overall, and I create a couple widgets so during the day I get some nice information while my phone is charging on my desk.

There was/is a shortcuts client/server app where it would run things periodically for you

But as others have said - women’s shelter, sell it, etc.

airgapped 2FA

I have a graveyard bin of old cellphones going back to flip phones and the Nokia tank