That's a standard feature available in any ROM.
That option is in
Wi-Fi preferences >> Advanced >> Install certificates, so was it not working?
You have asked about my findings concerning ArrowOS + microG in the TWRP thread, but my reply is better suited here.
Thanks, @SkaboXD. Kind of. I specifically mentioned I want to avoid proprietary GApps. And assessing programs list one could tell that I prefer Free (as in Freedom) and OpenSource programs.
Also, I have very serious privacy and safety concerns installing custom kernel. I trust AOSP much more.