No.
Stock recovery can only install official updates zip files, approved by OEM.
To install anything unofficial, like OpenGApps, you need a custom recovery, like TWRP.
BTW, I never get the sideload feature of official recovery to work in any phone I tried it (not much to tell the truth, but looks like a fake feature).
Thank you! I wanted to install gapps on omni treble gsi...
Solved by copying zip to system partition, installing twrp, formatting data, installing gapps with twrp, reinstalling stock recovery and formatting data again with stock recovery...
What a waste of time... Hope we will get a working twrp soon.
Btw. have you tried to use the phone unencrypted with rooted stock kernel? With editing vendor > etc > fstab.qcom forceencrypted to encryptable it works, but without wifi in rom.
The question is: will reflashing the stock kernel/recovery heal that wifi problem? I would try, but right now everythin is set up fine - perhaps you already tried...
If that would work, then it would be easy to use twrp. Then you only would need to change the boot.img after using twrp...
