dkms builld fails on an old Raspi B Model 1

[btreut]

trying to build the driver on a "Raspberry Pi Model B Rev 1" running under Raspbian 10 (buster) fails with the following contents in /var/lib/dkms/rtl8821CU/5.2.5.3/build/make.log

DKMS make.log for rtl8821CU-5.2.5.3 for kernel 5.10.17+ (armv6l)
Tue May  4 16:55:59 CEST 2021
make ARCH=armv6l CROSS_COMPILE= -C /lib/modules/5.10.17+/build M=/var/lib/dkms/rtl8821CU/5.2.5.3/build  modules
make[1]: Entering directory '/usr/src/linux-headers-5.10.17+'
Makefile:681: arch/armv6l/Makefile: No such file or directory
make[1]: *** No rule to make target 'arch/armv6l/Makefile'.  Stop.
make[1]: Leaving directory '/usr/src/linux-headers-5.10.17+'
make: *** [Makefile:1923: modules] Error 2

thanks in advance for any help ...