There has never been an update that breaks the WIFI/Hotspot, it is already broken and it is during the reboot procedure that it detects the fault and disables the module.
The list of your problems makes me fear the worst because restarting, no X mode, switching from SIM1 to SIM2 probably indicates a hardware problem. (I'm surprised that you don't have a problem with the fingerprint reader, often linked to SIM malfunctions) Poor and unstable performances are "Normal", ASUS has deliberately broken them by reducing the frequencies beyond 39-40° since firmware A11 .57 / .86 for all applications launched by Armory Create
Since April 2021 except for a correction (that ASUS had made on APN!) and another on the Touch (which also worked very well before being broken) this company of .............. .. no longer fixes any bugs and adds no new VoLTE compatible operators, Android security patches have been the only elements of firmware for 8 months, the ROG 5/S/Pro series is brain dead, Bug Wifi 6, latency Wifi, performance, compatible USB Dock use, new GPU/Vulkan driver, new VoLTE operator, in short, nothing more to hope for, it will make a nice paperweight in a short time if it hasn't already been done.
That said, in order,
a) save the data you consider important on the Cloud or PC
b) checks the battery charge and charges it if necessary
c) turn off your phone.
d) Let it come back to room temperature (20-25°) if you had played before turning it off.
e) Turn it on again, don't launch any software, check if your Wifi is operational
f) If the Wifi is broken, refer to my 1st sentence
g) If it's ok, update this new firmware
In view of the bugs you list, before point (g), I will perform a factory reset then do the update, I believe more of a hardware problem (typical problem of people who put it in the pockets of pants ) but I could be wrong in this case you will find a phone that does not reboot, stay on the right Wifi and on the right sim)