I have no idea what EDL mode is but some googling led me to an open source utility [1] called "Sahara." I wonder if you could use it for recovery?
While it could be used to recover the phone, it requires a "programmer" program, which is signed by the vendor (Google, here) that hasn't been leaked.
Or, really, I should say that these programs should be made available as "software rights to repair".
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Some reading:
https://alephsecurity.com/2018/01/22/qualcomm-edl-1/
A more up-to-date open source tool:
https://github.com/bkerler/edl/
EDIT:
see also this sibling (to you) reply:
> It should be noted that devices that are hard bricked and in Sahara mode (Qualcomm USB PID 9008) and have secure boot enabled (pretty much EVERY production device) will only accept signed programmers. This means that it is not only device specific (i.e. MSM8x26,MSM8974,etc) but vendor specific as well (i.e. LG, HTC, etc) since OEMs generate their own private keys to sign all firmware images, including EDL images.
Google have _not_ released the signed firehose files required to be able to fix this.