Nice review, but on what base now the 3.5mm jack is considered outdated?
For example :
- in some old car stereo players there are 3.5mm input jacks but no bluetooth
- with that present and few good apps one can use it to create wave / square, saw and other type of signals that can be well used for test purposes. Right away I`ll give example what I used it yesterday : 120Hz sine sweep to adjust car sub woofer amp. And it was straight forward 3.5mm adapter to RCA. Job done.
- currently (2020) I use mine with android 10 and UI 2.0. Last security update(at the time of writing this) 1.10.2020.
Why something old and well working should be bad? Android 7 was small enough and if you have 2 or 3GB of ram it was fast and took below 1GB for the OS. Now, with 9 and 10 it require more CPU power, more ram and storage. Did one gain something "extra" from it? NO! But on Android 6-7 was still possible to have phone line call recording. Now is fucked up!!
And compared to Android 1-2, then it was colorful, with nice drawn icons and so on. Now we have only lines, squares, triangles.. Even the cave man try to draw pictures to show that he went smarter than the line draw predecessors.. 
Yes, it has only USB 2.0 but on tests of file copy it manage quite well and honestly what exactly you need speed for? For me is million times better that I can connect USB flash, USB keyboard, USB endoscope camera, USB redio scanner ans so on.
Memory? Yes not that big, but as user with 330 applications, most of them  for work can say is enough! Music, video, photos - on the microSD card.
Also, no word for the fact is has 2 sim slots. What in some point is handy too..
Removable battery is not the plus. It is GREAT plus for mother phone. You do not have to break your freakin` device into parts to do that. And when you buy spare one or two batteries you can travel in areas that not have power around for good some time.
For me the only two low points are :
- quite big and heavy, compared to Xcover 3
- the real cover is not as tight as one can expect and after year of use for sure will not be exactly pure water sealed. Also, all the holes hould have covers as on Xcover 2!

In my opinion Xcover 3 phone, as it was but with 3-4GB of ram and 32-64Gb of internal storage and max android 6 is the perfect one!

I use phones for outdoor work almost everyday and have to comment. You're missing at least two important points in this great review:

1) Wide bezels and not too large screen are good for outdoor phone: Most of modern cellphones are annoying to the point of being unusable one handedly because there is no way to hold the phone without accidentally pressing something or scrolling the screen (throwing the map off for instance).

Samsung is the least bad, but still too big. Motorola Droid 4 was just about perfect in size in this case. Ulefone armor for instance is so big it's just unusable for the job. Often you only have one hand to use the phone and have to move around holding it so you can take a peek when needed.

2) biometric recognition is useless for outdoor phone. You can't use it wearing gloves, it's slower and more difficult than just wiping screen open, and face recognition doesn't necessarily work always.

3) 3.5 mm jack is standard and not in anyway outdated. Still the only reasonable way to connect music devices together. Bluetooth systems are not mostly good enough, and good stereo system (or headphones) never really get out of date.