Thank you. I got my device back in June. So I should download that and enter “sudo ./mkimage.sh?” Are there any other packages I will need?
No, the link I showed is to the repository with the code used to create new system images. You do not want to create a new system image, so you do not need to run ./mkimage.sh. And if you do, don’t run it with sudo. 
All you should need to do is install the picotool package and follow the steps outlined under “Update Procedure”:
If you run into any further problems, please post them here. Thanks!
“sudo apt update” was the key. OLED status now shows “PREF1SYSR120240730.” Thank you very much for your help and patience, josch!