Ah, I see, you have answered my question. This sounds like a pretty silly requirement, but as I didn’t know about it until now, perhaps someone could tell me what the reasoning was for this requirement? Not that it is likely to change my opinion, I just want to know what the reasoning behind it was.
Semper Fi! 
I hope you mean DSL because you can’t be still using dialup.
Their original post about this from way back pre-9.1.5 states,
“The Battle.net Authenticator is available for mobile devices and is a simple and convenient way to secure your World of Warcraft account, but if you prefer not to use it for whatever reason, you will still be able to post groups that will have descriptions auto-populated (e.g. based on raid name and difficulty selected in UI dropdowns, or derived from the Mythic Keystone currently in your bags). Our goal is to clean up the Group Finder while trying to minimize the inconvenience to ordinary players.”
So, like I said, i didn’t think this was a problem unless you’re trying to put something like “BIG PUMPERS ONLY” or “2k IO required” or whatever people put.
" In addition, only accounts that have been secured with a Battle.net Authenticator and Phone Notifications can add custom text to the Pre-made Group Finder listing. If you don’t have an Authenticator or Phone Notifications, you can use the Pre-made Group Finder, but you will not be able to write custom text on your listing."
-Blizzard
So whats stopping you from using the group finder?
I suppose I’m one of the ‘lucky’ ones. I use one of the original authenticators. I don’t think they have them anymore but, in my case, I don’t need a cell phone to play wow. And, yes, I qualify as an old fart.
As to the OP’s problem, I think you can work with Blizz support to have the authentication removed.
They’re going all in on the Battle.net Mobile App too.
"The Battle.net Authenticator is now available within the Battle.net Mobile App. The Battle.net Authenticator provides two-factor authentication to keep your Battle.net Account secure. All users must migrate their Battle.net Authenticator to the Battle.net Mobile App by January 5, 2024, as the old Authenticator App will be retired at this time. "
Won’t let me input any group. All boxes have a lock beside them and no input of any kind like what dungeon your running.
Yes, my last two were prepaid phones and authenticator worked just fine
All the more reason these kinds of threads are so silly… all this quibbling over something that costs like $30-$50 
Meanwhile, no one makes one peep about $80-$100/month internet bill (to play the game) or the $100-$200+/month electricity bill (to power the desktop or laptop)… but willfully choosing to not own a smartphone in 2023 is some sort of “hill to die on” I guess 
Are you talking about the old Authenticator App or the Battle.net Mobile App?
“What…you guys don’t have hills?”
It’s the link your sent to when you want to unlock the 4 extra pack spaces. Sends you to the Mobile app.
From what I remember the Battle.net app worked fine as well, although back then the Bnet app and the authenticator were still separate apps
Honestly basic burner Android smartphones are sooooo cheap nowadays, I suspect the people making these threads are assuming you need some high-end $1000+ iPhone to do even basic tasks… but that’s simply not true
A budget-variety $50 Android smartphone can do basically everything you need - and if having the ability to edit M+ listings is the main gripe, you can pay for like 1 month of service (to get the authenticator set up), put it in a closet/put it on a shelf somewhere, and never touch it again other than to get authenticator codes
My previous burner smartphone cost me a whopping $60 and I used the phone daily for like 4 years before I dropped it getting out of my car/cracked the screen and had to go shopping for a new one
So what are you trying to create a group for? I know you can list a keystone group without it, it fills in the dungeon and level of your key automatically. You just can’t add any custom text.
Baffling that some folks decide against getting an authenticator. Why risk not having one?
Under the premade tab then dungeons, you can put in the dungeon and the mythic but you can’t input text like the lvl your running.
Most cell phone providers are BEGGING you to take a free phone with you with a 12-month plan. Which do not cost an arm and a leg if you only get limited data.
Do you have a key?
If you have a key in your bag it should choose the dungeon and put the key level in the title automatically.
I’m more baffled by people still not owning a smartphone in the year 2023 tbh 
Like I said, it’s just such a strange “hill to die on” when these same people have no qualms with paying $100+/month for hi-speed internet, $200+/month for electricity (to power the gaming PC)… but paying like $30/month for basic cell phone service is apparently some kind of deal-breaker? 
I take business calls on my landline.
I’m baffled by people who are so concerned that other people are not paying for a cellphone contract and constantly texting and playing mobile games. What’s it to you if I decide not to spend hundreds of dollars to have a cellphone I would barely use? Are you getting a kickback for trying to market cellphones or something?
Not sure where you got that pricing, that’s not what a contract costs. Oh, you mean a phone you can only make calls on? Is that what you have? What good is that?
It is incredibly bizarre. I mean, the ONE piece of modernity I have resisted is a Kindle. I want real books. But I understand that I will then not have instant access to whatever I want to read.