I think Ukraine may be a way tougher nut for Russia to crack now, esp with their growing capability with Turkish-built drones, which proved themselves so effective in Nagorno-Karabakh (armour, trucks, artillery, sheesh the operators even got so bored they started picking off individual troops in foxholes). Just have a fleet of these patrolling up and down the border, ready to plink anything which crosses the line.
They might be better employed taking out rail, tunnels and bridges to hamper the resupply routes?