Command "allow-roaming=yes" on the lte interface of R11e-LTE miniPCI-e card is ignored in RoaterOS 6.41.3. Is there a way to turn on roaming by an init command on R11e-LTE? (As it is possible for example on Huawei ME909u-521). Is there some init commands reference manual avaiable?

make sure you have sim card inside.
Try to enable the lte,!raw logging topic and check if the dial sequence works ok.

Thanks, problem solved, when I inserted SIM card, then the command "allow-roaming=yes" was accepted. It would be nice to add such notice to the manual on wiki.mikrotik.com/wiki/Manual:Interface/LTE