Some reasons why I think this is an issue with the firmware of the Tuleta:


1. MAAS is already configuring "Lan_Privilege_Limit" to  "Administrator" for each BMC.  The documentation states-

# For IPMI over LAN access for a username, set "Enable_User" to "Yes", 
# "Lan_Enable_IPMI_Msgs" to "Yes", and "Lan_Privilege_Limit" to a privilege 
# level. The privilege level is used to limit various IPMI operations for 
# individual usernames. It is recommened that atleast one username be created 
# with a privilege limit "Administrator", so all system functions are available 
# to atleast one username via IPMI over LAN.


2. Below is part of the output of `bmc-config --checkout` for a working BMC.  This shows us the settings that MAAS is
   creating by default.

Section User2
	## Give Username
	Username                                      maas
	## Give password or blank to clear. MAX 16 chars (20 chars if IPMI 2.0 supported).
	## Password                                   
	## Possible values: Yes/No or blank to not set
	Enable_User                                   Yes
	## Possible values: Yes/No
	Lan_Enable_IPMI_Msgs                          Yes
	## Possible values: Yes/No
	Lan_Enable_Link_Auth                          No
	## Possible values: Yes/No
	Lan_Enable_Restricted_to_Callback             No
	## Possible values: Callback/User/Operator/Administrator/OEM_Proprietary/No_Access
	Lan_Privilege_Limit                           Administrator
	## Possible values: 0-17, 0 is unlimited; May be reset to 0 if not specified
	## Lan_Session_Limit                          
	## Possible values: Yes/No
	SOL_Payload_Access                            No
EndSection

As we can see we are creating the maas user with Administrator privileges.

For the machine that we are seeing issues with we get-

ubuntu@autopkgtest:~$ sudo bmc-config --checkout -D LAN_2_0 -h 10.245.143.113 -u maas -p bBfqnAAfllCf4H
ipmi_cmd_get_sol_configuration_parameters_sol_payload_channel: session timeout


3. bmc-info command for the machine causing issues.  Shows the machine is up and running:

ubuntu@autopkgtest:~$ sudo bmc-info -D LAN_2_0 -h 10.245.143.113 -u maas -p bBfqnAAfllCf4H
Device ID             : 32
Device Revision       : 0
Device SDRs           : unsupported
Firmware Revision     : 8.61
Device Available      : yes (normal operation)
IPMI Version          : 2.0
Sensor Device         : supported
SDR Repository Device : supported
SEL Device            : supported
FRU Inventory Device  : supported
IPMB Event Receiver   : supported
IPMB Event Generator  : supported
Bridge                : supported
Chassis Device        : unsupported
Manufacturer ID       : IBM Platform Firmware Division (42817)
Product ID            : 306
Auxiliary Firmware Revision Information : 00000000h

System GUID : 902b4c94-be98-a60b-01da-a86497788eb4

Channel Information

Channel Number       : 1
Medium Type          : 802.3 LAN
Protocol Type        : IPMB-1.0
Active Session Count : 2
Session Support      : multi-session
Vendor ID            : Intelligent Platform Management Interface forum (7154)

Channel Number       : 1
Medium Type          : 802.3 LAN
Protocol Type        : IPMB-1.0
Active Session Count : 2
Session Support      : multi-session
Vendor ID            : Intelligent Platform Management Interface forum (7154)

Channel Number       : 1
Medium Type          : 802.3 LAN
Protocol Type        : IPMB-1.0
Active Session Count : 2
Session Support      : multi-session
Vendor ID            : Intelligent Platform Management Interface forum (7154)