Hi,
I was looking for the documenation where to put the keys and I found this page:
https://openwrt.org/docs/guide-user/luci/getting_rid_of_luci_https_certificate_warnings
however IMHO there is an error there.
The certs should be here:
/etc/uhttpd.crt
and here:
/etc/uhttpd.key
unlike the above link says: (Option B): /etc/ssl/....