Identify Garmin's Owner. Person is dead :(

Hello!

First of all excuse me, some details may be a bit too personal and explicit.

The story and the problem:
In Ukraine, during the war on the battlefield a soldier was found (about 1 year after his death). 
The only "identifiable" thing with him - was a garmin Fenix 6 Pro (SN 3362034190)
with him, and no other possible ID's.... no phone - nothing.....

We want to find relatives so they can have "killed in action" status for his son(brother or whatever) and some benefits with this status (of course nothing can replace human)
current status is "missing in action" and it gives nothing to his family. We want they can bury his relative with honor and just to know the truth.

The watch has no activities or records on it.

We(Me and some friends) tried to:
- add wifi to soldier's watch
- do some special activity on 2 watches (one is ours), 
- create special segment on Strava
 - We hoped for 2 users appear on the segment participants list (no success)
We tried to see emergency contacts - but it's empty.

It has only "settings.fit" with some info - 80kg weight 2m height and 1997 as a birth year

Few watchfaces and data fields in the APPS folder.
Local dealers says "bought somewhere else" and repair services (official and non officials) don't have any info for Serial Number.
I contacted Garmin also,
Maybe relatives still have access to his relative's e-mailbox - so Garmin can send email to owner's box, give my contacts to them, if they want to contact - they surely will do.
Any ideas more ????
PS: I even tried sniff wifi traffic  - of corse TLS encrypted and no user_id cookie inside request...