As an alternative to the standard Advantage & Disadvantage rules, a group might instead make use of the idea of Boons & Banes. Under this rule, circumstances can make d20 Tests easier or harder, with positive circumstances adding one or more Boons, while negative circumstances impose one or more Banes.
Boons improve your d20 Tests. One or more boons might apply to a given roll. For each Boon, you roll a d6 and then add the highest number rolled on all the boon dice to d20 Test. For example, if you make a d20 Test with 3 boons, you would roll 3d6. Say you get 1, 4, and 6 on those dice. The 6 is the highest number, so you add 6 to your d20 Test.
Banes hinder your d20 Tests. One or more Banes might apply to a given Test. For each Bane, you roll a d6 and then subtract the highest number on all the bane dice from your d20 Test. For example, if you make a d20 roll with 4 banes, you would roll 4d6. Say you get 1, 3, 5, and 5 on those dice. Since 5 is the highest number, you would subtract 5 from your d20 Test.
Boons and Banes cancel each other out, one for one. If 2 Boons and 1 Bane apply to a particular d20 Test, you make the roll with 1 Boon (1 Bane cancels 1 Boon). Similarly, if 2 Boons and 4 Banes apply to the Test, you would end up making the roll with 2 Banes (2 Boons cancel 2 Banes).
The purpose of this system, as opposed to Advantage & Disadvantage is to increase the granularity of d20 Tests by taking a more thorough accounting of circumstances that might influence the test being made. It also neatly sidesteps around the standard rule with Advantage & Disadvantage that states that if you have both Advantage & Disadvantage, regardless of the source and how many of each could be applied, the roll is ultimately made without either being applied.