Only titleId [mediaType [launchFlags]] is supported, and the launched title shouldn't rely on APT and all 3 parameters should be hex-encoded.
usage example, with titleId+mediaType:
(gdb) set remote file-exec 0004013000003702
(gdb) r 0
The physical memory access "bit31" mapping (0--0x30000000 => 0x80000000--0xB0000000) as well as privileged (kernel) mappings confuse debugger clients like IDA's which interpret the value of the registers.
Access to those mappings can be toggled using "monitor toggleextmemaccess" instead (issue reported by @Nanquitas). Closes#943.
Additionally, support for the buggy IDA 6.8's buggy gdb client was removed. Please use IDA 7.0 or higher.
P.S: IDA 7.0 added client support for no-ack mode (Debugging options > Set specific options), which should be enabled to make debugging twice as smooth. "Use stepping support" should be unchecked.