The idea of a straight pull bolt action is neat, elegant, and seems like it ought to be a world beater (in its class), but somehow, historically, that never quite happened.
The names that come to me, off the top of my head are Ross, Lee, Schmidt-Rubin, and Browning. I'm probably missing some, but those are the "big" ones I remember.
The Canadian Ross, and the American Lee-Navy were used in service, but despite some love by the users were not considered successful enough for the design to be retained for future use.
The Swiss, on the other hand, kept the straight pull system, improving their original design in later models, and only switched to the semi auto /select fire rifle after WW II. The Swiss are tremendous weapons designers and makers, but historically, have not had to be major weapons users.
One of the reasons straight pull bolt actions have not been tremendously successful is because they are more complex and more expensive to make than traditional bolt actions. And they are not able to apply the same force to camming the bolt open, or closed as the traditional bolt action.
To a 1900s era military these can be very large considerations.
So, with a traditional bolt gun (Mauser, SMLE, Moisin-Nagant, etc) being thought to be at least slightly superior in the slop of infantry combat, as well as being simpler and cheaper, the slight speed advantage of the straight pull lost out.
Browning made a really neat straight pull .22LR for a time. called the "T-bolt". Never a huge commercial success, probably because it cost more than its competition's semi autos...
As a straight pull bolt action, the AR has a built in drawback, the charging handle. Compared to some other guns, its rather flimsy, and in a horridly poor spot, (ergonomically) for constant use (every round) AND, it only works one way.
I do not know about the "side charger" AR uppers, does their handle work both ways? Or does it also rely only on the spring to close the action?
Left side handle, isn't it?? Also not the best spot, but less awkward than the standard AR set up.
If you're looking for a military style rifle that can be manually operated as a straight pull action, look at the M1A.
Not cheap, I grant you, and maybe difficult to get in Europe, but it is made to have the gas system turned on and off at the user's desire. The gas system is meant to be turned off when firing rifle grenades (using blank cartridges) and all it takes is a screwdriver, (or anything else that fits in the slot, bayonet, case rim, coin, butter knife, etc.
)
Serious rifle in a serious caliber (7.62 NATO) so costs more than ARs and smaller caliber ammo, may not suit your needs, but it is one rifle I can think of that can be either semi or a straight pull manual, (and could be switched every other shot if you want) that doesn't need any modification in order to do it.