Apparently if you build the ue5-main branch from source, it will work with XCode 13. Currently waiting for it to build, thus far about 50% done after 1 hour building on 10 core M1 Max.
Source 1, includes some instructions:
Source 2 (anecdotal evidence):
Also note:
The git clone step can take an incredibly long time, I recommend using something like the following to only do a shallow clone of the single branch you need, into a new directory:
git clone --depth=1 --single-branch -b ue5-main git@github.com:EpicGames/UnrealEngine.git UnrealEngine5
Note I cloned this into a new UnrealEngine5 directory, rather than using an old 4.x directory.
YMMV but for me, creating a new shallow clone was (surprisingly) much, much faster than fetching and changing branch from an existing clone e.g. git fetch && git checkout ue5-main.