I don't think you'll find one without fitness functions, but on all of them you can largely ignore the fitness functions.

For mapping, what functions do you need, and what's your budget? You can get cheaper units that just show a map (and perhaps overlay a preplanned route) o'r more expensive units that do true satnav-style navigation and can re-route on the move (eg Hammerhead). Knowing your budget would make this easier.

(And with all that said, probably your best option is an old Android phone off eBay and a handlebar mount to run one of the many mapping programs)

Easiest solution is to use an old phone or buy a cheap old phone off ebay/whatever and use that in airplane mode as a gps.

If you don't need fitness tracking, maybe just a straight up GPS unit?

dcrainmaker.com has well researched reviews, maybe you can find what you are looking for there. The site does have a feature comparator section somewhere.

All I need is good GPS/mapping features that doesn’t connect to my phone what so ever.

As others have pointed out, a throwaway phone would likely work best for this use case.

I use an old Samsung phone with OSMAnd (uses Openstreetmap data), but it can also run whatever other mapping software I could possibly need. For example, we had a local community ride, and they required us to use Ride with GPS, which I never used before. No problem. A bike computer with GPS nav would have made this more difficult.

If you plan to ride for more than 3-5 hours at a time, a phone may not be best, unless you've got it connected to a powerbank.

I have a watch that can track my cycling using GPS. It then syncs with my phone, but I don't have to have the phone when I am riding.

It's an Amazfit BIP, 5 years old and still running fine, under $100, and a charge lasts for up to 6 weeks.

https://www.rei.com/c/cycling-computers

There’s a selection here that all look pretty decent

Garmin etrex series. Fairly cheap, runs on AA batteries (great for travelling, i packed 3x2 batteries at some point and was good for 5 days of hiking without recharge). The screen is not the biggest, but always worked for me. No Bluetooth or Wifi. Bike mount is ok, not as good as the bile specific ones. You'll need to upload a map yourself via USB as well as tracks etc.

I would not recommend it for non tech savy users (devices with a companion app are easier to setup and load with tracks etc.). That's actually the reason I'm considering switching to a wahoo device