The last link you posted is of two blokes who are full members of the Ukrainian military, one I know was a member before the recent invasion by Russia.Leverage and optics.
two sides of a similar coin:
and sorry to link a Daily Wail, but that's the exact point:The latest targets also include the new Russian-backed mayor of the Ukrainian city of Melitopol.www.politico.eu
Scott Sibley, a veteran of the British armed forces, has been named by friends as the Briton who died in Ukraine.www.dailymail.co.uk
Shaun Pinner, 48, and Aiden Aslin, 28, have been taken captive by Russiawww.independent.co.uk
Sure, one can discuss the nuanced difference between contractors, advisors, trainers, mercs, and BATT,
but this is also a war of appearances, and twitter/telegram posts.
In a war zone wearing kit with a Royal Marine Commando patch, and a Union Flag - what does that look like? What can it be made to look like? Can be advantageous to either side.
The second link also shows a former british soldier who joined the new Ukrainian military unit for foreigners.
All in all none meet the requirements to be classified as mercenaries, no matter what the Russians say.