Everybody who would like to activate aptX for Bluetooth on macOS 11 Big Sur again can do that relatively easily. The process is just a bit annoying.
As already with macOS Catalina it could happen that the Bluetooth connection was not established with the to AAC compared better aptX standard. You could check this by alt-clicking on the Bluetooth symbol. This does not work anymore. So it is not possible to find out which standard the Mac is using.
You have to download a software tool from Apple’s developer area and then monitor the data rate and if necessary force the aptX standard. A completely absurd process, but somehow Apple doesn’t know if the supported aptX standard should be used or not. In the end it will only be made available to tinkerers.
The complete procedure is completely congruent with the one under macOS Catalina, which is why we simply refer to the older instructions for reactivating aptX.