Hello Friend.
Actually I want to use Mikrotik LHG for use in Band 42 ( 3500Mhz),
AS you know the the only LHG 4g Kit can support this frequency, but this device discontinued.
now I want to know , is it possible that buy "LHG LTE kit" and replace the PCIE modem with "R11e-4G " miniPCIE modem that support B42(3500Mhz).( I found a "R11e-4G " in market )

Yes it's possible replace that LTE module.

But is sad to see how MikroTik discontinued product without a replacement like on this case.

On my case is the same with Band 4. R11e-LTE-US discontinued but no replacement by MikroTik.

Regards.

Thank you so much for your good feedback
now I think I can solve my problem

but an interesting question is in my mind.
is it possible to replace that modem with some other brand of MINI-PCIE modem ?

Yes, but not all cards are compatible.

Regards.