Proficiency Bonus

This is an optional rule described in the Dungeon Master's Guide 
In Campaign 3.  This is an optional rule that you can choose to use.  It will require more math since you can't do this on DNDBeyond.  Also be sure to not use the plus from the skill in DNDBeyond, but the plus from the stat + the Proficiency die + the d20.

Proficiency Dice

This optional rule replaces a character’s proficiency bonus with a proficiency die, adding more randomness to the game and making proficiency a less reliable indicator of mastery. Instead of adding a proficiency bonus to an ability check, an attack roll, or saving throw, the character’s player rolls a die. The Proficiency Die table shows which die or dice to roll, as determined by the character’s level.

Whenever a feature, such as the rogue’s Expertise, lets a character double his or her proficiency bonus, the player rolls the character’s proficiency die twice instead of once.

This option is intended for player characters and nonplayer characters who have levels, as opposed to monsters who don’t.

Proficiency Die

Level	Proficiency Bonus	Proficiency Die
1st-4th	+2	1d4
5th-8th	+3	1d6
9th-12th	+4	1d8
13th-16th	+5	1d10
17th-20th	+6	1d12