Fenix 6 Pro GPS Problem accuracy

No, i didnt. I would like to try a dual-band BT tracker with own inbuilt battery and with small size but unfortunately doesnt exist on the market yet such a device just professional ones but those are big , have modular design and very expensive...

It is not the complete list (not an easy task! :) but all phones with Snapdragon 765G, 720G, 765, 662, 460 , 855, 855+, 865 are dual-band capable, the Kirin (Huawei) 980, 990 chipsets also support it and the Mediatek 1000 also. There are phones with additional GPS chipset like MI8 as i wrote and Lenovo Z6 with an Allystar GPS chipset but the Lenovos have so bad ROMs and support that Lenovos are strongly NOT recommended mobiles, one of the worst on the market... :D

try to check the SOC of the selected phone on gsmarena.com , that will help

i prefer to choose a Xiaomi model (and the Redmi sub-brand is the cheaper ones), those have very good ROMs (and its support is also very good). the Redmi Note 9S / Pro is one of the cheapest as new with 720G

And one more important thing, on US's territory the Galileo's reception in many mobiles (especially the US models for US market) is still blacklisted (but outside these are working fully)

Great, thanks for the list ! GSMArena lists some phones that should be compatible, but it's not working all the time I think. The samsung S10 can use dual band, but not all models with the Snapdragon can do it though. It's not easy ;)

But your list will help. I think I will go with the cheap Mi8 solution, it's 150€. Otherwise I could replace my main phone (samsung S10), but the budget is completely different ha ! 

ANother question, it's not because a phone can receive dual band that all GPS app will use it, right ? The one you shared can use it, but all sport apps may not be as clever ? Or is it automatically used as long as the hardware supports it ?

Fenix 6 pro with gps only mode:

Yeah, sometimes they race to be worse...

Normal for the tracks among buildings, but bad around the pitch.

I've been thinking of upgrading from my vivoactive 3 to the fenix 5s pro. But yikes, these complaints are not encouraging. So I just checked my v3 for distance and, secondarily accuracy, against my phone on a short cycle with two legs. I use a flatbar bike, so the watch faces up. On the first leg, my OnePlus 7 using a komoot app registered 1.82 km; the V3 1.83 km. On the second leg, both the phone and watch posted 5.15 km. Over the 7,017-metre total, they apparently differed by ten metres.

As for accuracy, sorry I don't have maps to post so I'll just describe the two as there were minor differences. At one point, the phone showed my downhill track temporarily crossing the uphill one, though that never happened. The watch correcting showed the downhill track on the right side at that stretch. Further down, both cut the corner of a turn, the watch slightly worse. for the last km or so, the phone was well to the left of the mapped road, from five to ten metres at a guess. The V3 watch was on the road this whole stretch and hit the final intersection bang on. Near the end, the phone was definitely offtrack by (guessing here) about ten metres. The watch, which displays on gmaps, was within a metre or two. I don't know what map app Komoot uses.

I can't verify the elevation as I started the V3 at the beginning of the ride but not the phone till I was in 4.19 km but failed to note the elevation at that point. All other numbers above reflect that difference. I had the vivoactive 3 set to GPS only.

For now, I'll stick with my V3 as gps accuracy is important to me.

If you are primarily using the GPS on your bike I don't think you will have a problem.  Most of the reports I have seen on the forum where people are having GPS accuracy issues are slower (run, hike, etc.).  Due to the higher speed and face up positioning, you are probably safe.  My 2 cents at least.