Olde Swords Reign is a tabletop roleplaying game based on 5th Edition but designed with emergent gameplay in mind. It's faster, a tad deadlier, and relies more on player creativity to problem-solve than the options on a character sheet.
Universal mechanics run through the game that speed up gameplay, make improvisation easier for both players and GMs as well as helping to make rulings a little more intuitive and consistent.
You can pick up and play any old-school module or OSR adventure but still have that 5e framework.
Being based on the 5e ruleset, it can be played with any of the bigger Virtual Table Tops (VTTs) that have 5e rulesets and most of the rules can also be easily dropped into your regular 5e game.