QF have used it sporadically when circumstances have resulted in shortage of line F/Os and/ or excess Captains. Extra training for the concerned. PM only on line ops. No recency requirements except for a reaccreditation sim each year.
Same at my airline
10 minutes in the RHS during recurrent SIM training (V1 cut, turn downwind, hand flown engine-out ILS to a landing) enables a captain to be rostered in the RHS should the need arise
When the practice was implemented over a decade ago, most viewed it as a management hedge against junior pilots engaging in a union-sanctioned job action
Today, is is more likely that a worsening shortage of F/Os will be the reason
Should it occur, RHS PM duty only, like the previous poster I would assess the greatest hazard to be a mild CRM challenge during flight and a botched logbook entry post-flight
Fly safe