That is the correct SHA1sum for that file, not sha256sum
What is you currently firmware? Which version on OpenWrt & LuCI?
Did you get that checksum from LuCI?
I have never heard that SHA1 checksum would be calculated by OpenWrt or LuCI, as earlier there was just MD5 checksum, and then it was switched to SHA256 (and I added support for LuCI to show both). So, you getting SHA1 is interesting (if your checksum is shown in LuCI).
Note that you can also calculate the checksum by outside tools. (I just found your SHA1 via hashcalc in PC.)