What are the tournament rules for main deck and sideboard size in Riftbound, and when can sideboard cards be swapped?

Ruling: In tournament play, the main deck must be exactly 40 cards (not "at least 40" as in core rules). The sideboard must be exactly 0 or 8 cards. Sideboard cards can be swapped between games within the same match (BO3), not just between different matches/opponents.

Sequence:

• Game 1 must use your officially registered deck list
• Between games in the same match, you may swap cards between main deck and sideboard
• Your deck must return to the registered configuration at the start of each new match

Nuances:

• Tournament Rules add restrictions on top of Core Rules (Core Rules allow "at least 40", Tournament Rules require "exactly 40")
• The sideboard can only consist of valid main deck cards
• Limits on copies of named cards apply to the combination of main deck and sideboard
• Your registered deck list includes which champion is your Command Center