After reading a post on Roll20 from a player needing help with classes in a very low magic setting for their D&D game I was inspired to try my hand at a few options. I'm going to note right up front this would be for a game where magic is not in the hands of the players and right off the bat that means Wizards, Sorcerers, Druids, and Warlocks are 100% off the table. Designing a Wizard without spells is called crumpling it up and throwing it out completely. So that leaves us with classes that would still have a place in a world without magic: Bards, Barbarians, Clerics, Fighters, Monks, Paladins, Rangers, & Rogues. I also want to note that this is given the options available from the 5th Edition PHB and nothing else.
The Easy Ones:
I'm not going to break these ones into "new class options" as none of them require magic though it will limit what sub-classes are available:
Barbarian: Barbarians are tough, but not (Usually) because of magic, just don't allow the Totem Warrior and you'll be fine. (I will note that the other option, Berserker, isn't greatly designed and leaves the Barbarian feeling like there should be more, but when you remove magic the ability to take half damage from most sources while raging makes this class incredibly powerful)
Fighters: Just don't allow Eldritch Knight simple as that.
Monk: This one is more limited as only Way of the Open Hand would be available.
Rogue: Just don't allow Arcane Trickster and you'll be fine.
A Class By Any Other Name:
Some classes fit thematically without actually NEEDING a whole class of their own and can have all their flavor without adding new rules.
Cleric: Without their magic a Cleric is just a holy hero. While they cant take many shapes that usually reflected domains without the actual spells this can actually be covered instead by a player's background. Any player regardless of class with the Acolyte background can consider themselves a Cleric of their chosen god. Anyone who says a Cleric and a priest aren't the same I have to say without the divine power of their god yes they are.
Paladin: There was a time that the best way to make a paladin was by being a warrior that took up holy powers. While over the years they have become a much more distinct class mechanically in its roots a Paladin was the "Holy Warrior" of the world. Given what I already pointed out about clerics this makes creating a Paladin easy. Just become a Fighter and take the Acolyte background. All your oaths and religious duty that many see a paladin as needing is just something you can RP out and without magic powers to be taken away the repercussions of going against your faith is the same as any other holy man, being excommunicated from your church.
The Over Hauls
These classes are the ones that have magic as a major part of their mechanics, but even with them stripped out still provide a lot to offer the word. Some have themes that can be picked up with backgrounds, but the real meat of the class as well as some of their iconic natures that aren't lined to magic would be lost.
Ranger: The easy answer is just making anyone that takes the Outlander background be a Ranger, but that only covers the tracking and foraging potion of the class. Luckily WotC did the heavy lifting on this one and made a magic free Ranger a while back HERE
Bard: Just like the Ranger, a Bard COULD be made thematically by just taking the Entertainer background, but what about the skills monkey that is a little good at everything or the musician that actually bolsters their allies. For that we need something. Unlike the Ranger however, who is only a 1/2 caster, the bard is considered on par magically with a wizard and cleric meaning removing spells removes a TON of the class and creating filler to compete will be mostly remaking the class. So what do we do? The answer is in the sub-class mechanics of 5e. Bards and Rogues already share a high skill list and the Expertise class ability as well as similar armor and weapon proficiencies making it the perfect place to make OUR Bard.
The Bardic Roguish Archetype
Again I want to note this is a class option for the Bards as a class are off the table. If not this is going to step all over the "real" Bard and even potentially outshine them in some of their abilities.
Musician: At 3rd level you gain proficiency in the Perform* skill as well as two musical instruments.
A Bard may also take expertise in any Instrument similar to Thieve's Tools
Jack of All Trades: Due to your wandering and curious nature you have at least a little knowledge in most everything granting you half your proficiency bonus in any attribute bonus you do not already gain proficiency.
Inspire Greatness: By 9th level your musical prowess has reach the point as to bring the best out anyone perform for. As an action you can being singing a song of greatness about a single ally. While the ally is able to hear this song they gain Advantage on all Ability Checks and Saves. You can continue this song over multiple round (To a maximum of 10 minutes) by expending your action each round to continue playing. If you take damage while performing you must make a Performance/Instrument (Charisma) check equal to half the damage taken or 10 (Which ever is higher) or be interrupted. Once this song is ended or interrupted you cannot inspire such greatness again until after a short or long rest.
Greatness in Battle: By 13th Level your Inspire Greatness reaches new heights providing Advantage on Attack rolls in addition to its other benefits. Being interrupted doesn't mean the show is over anymore either as you can now Inspire Greatness a number of times equal to your Charisma modifier (Minimum 1) before needing to take a short or long rest. Additionally, while maintaining your song as a bonus action each round you can change the subject or your song transferring the effects to a new target. Only one target may still gain the effects of Inspire Greatness.
Mass Appeal: At 17th Level you can inspire more than just the subject of your songs. You Inspire Greatness ability now affects all allies who can hear and see you. Additionally if you start your performance before Initiative is rolled everyone under its effects gains a bonus to Initiative equal to your Charisma Modifier.
*The Performance Skill is the use of vocal or dancing in place of an actual instrument and any time a player may choose an instrument to be proficient in may choose Performance instead.
Personally I like magic in my games, but I hope this helps some of you looking for a more grounded setting for you tabletop needs. I know the cleric and Paladin are a bit of cop outs, but they do work and maybe if this gets enough attention I'll flesh out something a bit more special similar to what I did for Bards.