Hunter Biden was involved in criminal activities. He knew he was because he asked his accountant to tell him what his income would be if he was in jail. It’s probable that his father, VP Biden, knew this as well.
Hunter Biden’s accountant Eric Schwerin sent Hunter a reply to how much income he could expect to make in 2017 even if he had to go to jail. Schwerin responded that Hunter could conservatively estimate around $750,000 annually, even if he went to jail:
The fact that Hunter was worried or concerned about going to jail says something – that he was aware that he was doing something illegal and that he could go to jail for doing.
We don’t know all that Hunter was up to specifically related to his concerns above but we do know that Hunter and his business partner Devin Archer were copied on the announcement that then Vice President Joe Biden was traveling to Ukraine.