Using https://tobtu.com/lmntlm.php I can turn František1 into the NTLM hash 902BD6FDDF5248CE7902174E408F3F1F which means your NTLM-hash is correct.
You also say you used ?b?b which did not lead to hashcat cracking it.
I too tried ./hashcat -a 3 -m 1000 902BD6FDDF5248CE7902174E408F3F1F Franti?bek1 and ./hashcat -a 3 -m 1000 902BD6FDDF5248CE7902174E408F3F1F Franti?b?bek1 but hashcat did not crack it.
If I make a NTLM hash of a variant without unicode char: Frantisek1 (64436D005F319C8AC790209424608CD2) and run ./hashcat -a 3 -m 1000 64436D005F319C8AC790209424608CD2 Franti?bek1 then hashcat does find it.
This is very strange, maybe hashcat doesn't do unicode well?
EDIT:
also trying --hex-charset did not work, Franti in hex is 4672616e7469 and ek1 in hex is 656b31:
./hashcat -a 3 -m 1000 --hex-charset 902BD6FDDF5248CE7902174E408F3F1F 4672616e7469?b656b31
./hashcat -a 3 -m 1000 --hex-charset 902BD6FDDF5248CE7902174E408F3F1F 4672616e7469?b?b656b31
Nor does using ?h for hex chars:
./hashcat -a 3 -m 1000 --hex-charset 902BD6FDDF5248CE7902174E408F3F1F 4672616e7469?h?h656b31
./hashcat -a 3 -m 1000 --hex-charset 902BD6FDDF5248CE7902174E408F3F1F 4672616e7469?h?h?h?h656b31
You also say you used ?b?b which did not lead to hashcat cracking it.
I too tried ./hashcat -a 3 -m 1000 902BD6FDDF5248CE7902174E408F3F1F Franti?bek1 and ./hashcat -a 3 -m 1000 902BD6FDDF5248CE7902174E408F3F1F Franti?b?bek1 but hashcat did not crack it.
If I make a NTLM hash of a variant without unicode char: Frantisek1 (64436D005F319C8AC790209424608CD2) and run ./hashcat -a 3 -m 1000 64436D005F319C8AC790209424608CD2 Franti?bek1 then hashcat does find it.
This is very strange, maybe hashcat doesn't do unicode well?
EDIT:
also trying --hex-charset did not work, Franti in hex is 4672616e7469 and ek1 in hex is 656b31:
./hashcat -a 3 -m 1000 --hex-charset 902BD6FDDF5248CE7902174E408F3F1F 4672616e7469?b656b31
./hashcat -a 3 -m 1000 --hex-charset 902BD6FDDF5248CE7902174E408F3F1F 4672616e7469?b?b656b31
Nor does using ?h for hex chars:
./hashcat -a 3 -m 1000 --hex-charset 902BD6FDDF5248CE7902174E408F3F1F 4672616e7469?h?h656b31
./hashcat -a 3 -m 1000 --hex-charset 902BD6FDDF5248CE7902174E408F3F1F 4672616e7469?h?h?h?h656b31