Building modules, stage 2.
  MODPOST 6 modules
  INSTALL /home/d351d3r/backport-iwlwifi/compat/compat.ko
At main.c:160:
- SSL error:02001002:system library:fopen:No such file or directory: crypto/bio/bss_file.c:69
- SSL error:2006D080:BIO routines:BIO_new_file:no such file: crypto/bio/bss_file.c:76
sign-file: certs/signing_key.pem: No such file or directory
  INSTALL /home/d351d3r/backport-iwlwifi/drivers/net/wireless/intel/iwlwifi/iwlwifi.ko
At main.c:160:
- SSL error:02001002:system library:fopen:No such file or directory: crypto/bio/bss_file.c:69
- SSL error:2006D080:BIO routines:BIO_new_file:no such file: crypto/bio/bss_file.c:76
sign-file: certs/signing_key.pem: No such file or directory
  INSTALL /home/d351d3r/backport-iwlwifi/drivers/net/wireless/intel/iwlwifi/mvm/iwlmvm.ko
At main.c:160:
- SSL error:02001002:system library:fopen:No such file or directory: crypto/bio/bss_file.c:69
- SSL error:2006D080:BIO routines:BIO_new_file:no such file: crypto/bio/bss_file.c:76
sign-file: certs/signing_key.pem: No such file or directory
  INSTALL /home/d351d3r/backport-iwlwifi/drivers/net/wireless/intel/iwlwifi/xvt/iwlxvt.ko
At main.c:160:
- SSL error:02001002:system library:fopen:No such file or directory: crypto/bio/bss_file.c:69
- SSL error:2006D080:BIO routines:BIO_new_file:no such file: crypto/bio/bss_file.c:76
sign-file: certs/signing_key.pem: No such file or directory
  INSTALL /home/d351d3r/backport-iwlwifi/net/mac80211/mac80211.ko
At main.c:160:
- SSL error:02001002:system library:fopen:No such file or directory: crypto/bio/bss_file.c:69
- SSL error:2006D080:BIO routines:BIO_new_file:no such file: crypto/bio/bss_file.c:76
sign-file: certs/signing_key.pem: No such file or directory
  INSTALL /home/d351d3r/backport-iwlwifi/net/wireless/cfg80211.ko
At main.c:160:
- SSL error:02001002:system library:fopen:No such file or directory: crypto/bio/bss_file.c:69
- SSL error:2006D080:BIO routines:BIO_new_file:no such file: crypto/bio/bss_file.c:76
sign-file: certs/signing_key.pem: No such file or directory
  DEPMOD  5.3.6-1-MANJARO
depmod will prefer updates/ over kernel/ -- OK!
Note:
You may or may not need to update your initramfs, you should if
any of the modules installed are part of your initramfs. To add
support for your distribution to do this automatically send a
patch against "update-initramfs.sh". If your distribution does not
require this send a patch with the '/usr/bin/lsb_release -i -s'
("Manjaro Linux") tag for your distribution to avoid this warning.

Your backported driver modules should be installed now.
Reboot.