Believe it or not, those soldiers have mobile phones and the internet.
I suspect that this (in context of access to wider-world information
and dispiriting calls back home to their relatives) was actually a major factor in blaming soldiers' phones for the recent attack.
"It's for your own safety, and the greater good of Russia, to isolate yourself from everything but your military commanders!"
TBH, that's something all armies would prefer, and many tried, through blue-penned (or snipped out - so best only to write on one side of the paper) censoring of mail to and from the front-line as the compromise for morale reasons, both at the war-front and home-front. Which is the kind of industrial effort that has been grossly outpaced by the technical capabilities of livestreaming unfettered realities. State sanctioned channels of communications would be highly prefered by those at the head of of the war-machine, though not by those at the coal-face.
(...noting that a practically identical layout was used for "I am well" postcards from Pearl Harbor, immediately after the attack.)
And this all-in-one WW2 solution (US, but again pinched from us Limeys
) to bulk mail, with the anti-espionage 'features' of being duplicated beyond the means of using microdots/invisible ink that might escape the ubiquitous censors' strict and curt attention.
Though there were "Addressee code tricks" that you could still pull (developed from the ones used in the "pay on receipt" days of mail, to avoid shelling out on letters that already had conveyed their main message just by how they looked), if arranged in advance. e.g. if to "Mrs Martha Smith", your mother knew you actually were feeling well, "Mrs M. Smith" revealed that you had a non-worrying injury, and further variations on from there. (My google-fu is failing to find anything about it, within the mountains of info on how to send mail
to serving soldiers of various nations... But I'm sure it's a known trick. So much so that I wouldn't be surprised to hear that it has been 'locked down' by one or other military postal service by only allowing a 'registered' contact-detail to ever be used, per recipient, under the guise (maybe) of handy pre-printed stationary, per instance, "for everyone's convenience". Not that there aren't ways round that, of course.)