If you just strip all the muniversal shenanigans out of the Portfile, it builds just fine universal on BigSur Intel without any fuss.
K % uname -a Darwin MacBookPro-2012.local 20.3.0 Darwin Kernel Version 20.3.0: Thu Jan 21 00:07:06 PST 2021; root:xnu-7195.81.3~1/RELEASE_X86_64 x86_64 % port -v installed icu The following ports are currently installed: icu @67.1_3+universal (active) platform='darwin 20' archs='arm64 x86_64' date='2021-02-14T13:33:16-0800' % file /opt/local/lib/libicudata.dylib /opt/local/lib/libicudata.dylib: Mach-O universal binary with 2 architectures: [x86_64:Mach-O 64-bit dynamically linked shared library x86_64] [arm64] /opt/local/lib/libicudata.dylib (for architecture x86_64): Mach-O 64-bit dynamically linked shared library x86_64 /opt/local/lib/libicudata.dylib (for architecture arm64): Mach-O 64-bit dynamically linked shared library arm64
