+1 on codenames. I played the board game pre-covid and the current online version is browser based, robust, free to play with no ads whatsover (except for the phyical game itself) and no required signup.
Among Us is a great laugh, we did that as a team last week. Getting your colleague thrown out an airlock for a murder you committed yourself never gets old.
Is it mandatory? If you assume a staff member has x hours available each week for work, is this coming out of x (at the expense of company business) or is it coming out of 168-x (and thus reducing the staff member's time for sleep, shower, cooking, family, et c)?
I do them as part of work hours, and while not mandatory I do strongly encourage everyone to participate. I think the increased team cohesion is well worth 2 hours a month of "lost" productivity.