I know there are a lot of posts on here covering the "Invalid Firmware Upload To comply with regulatory amendments, we have modified our certification rule to ensure better firmware quality. This version is not compatible with all previously released ASUS firmware and uncertified third-party firmware. Please check our official websites for the certified firmware." but after reading those and troubleshooting the only solution is to grab a PC running Windows and it uploads the updated to firmware 386.5_2 no problem via Chrome. I tried Safari, Chrome, and Brave on my MBP running Catalina 10.15.7. I ran into this same issue with the previous firmware update but I'd like to find a solution so I don't have to grab a PC every time I need to update the firmware. I tried clearing the cache, and rebooting the router (RT-AC88U) but still had no success on my Mac via any of the 3 browsers. Does anyone have suggestions or further troubleshooting to find a solution for firmware updating on a Mac?