Could someone try to merge no outlines with 100% catch rate (it might worke) and generate the ips? (ips patches https://gbatemp.net/threads/batch-tool-to-generate-ips-patches-for-pkmn-su-mo.452178/)
I have the same problem since few days. And I think it is a problem with system/update(?). On my laptop I was able to upload .hex without a problem.
/EDIT
Be sure that you are selecting a good hex file.
Everything else is OK.
UNO R3 like this (microUSB) will also works: https://www.aliexpress.com/item/1pcs-New-2016-UNO-R3-ATmega328P-CH340G-MicroUSB-Compatible-for-Arduino-UNO-Rev-3-0-hei/32689124737.html