I searched a lot for a way to have the same lander multiple times for Multiplayer.

Found a solution with the current Version of the game.

Search for the startconditions.xml in this path "\SteamLibrary\steamapps\common\Stationeers\rocketstation_Data\StreamingAssets\Data"
The Drive letter depends on your system.

Open the startconditions.xml for Mars and Moon edit this section:

<StartCondition Id="Default">
<Name Key="DefaultStartCondition"/>
<Description Key="DefaultStartConditionDescription"/>
<PreviewButton Path="Interface/button_starting_standard.png" />
<Spawn Id="FuelTankInsulated" Event="NewWorld" />
<Spawn Id="DefaultLander" Event="NewWorld" />
<Spawn Id="LanderCapsuleSmall" Event="NewPlayer" />
<Spawn Id="DefaultNewPlayer" Event="NewPlayerKit"/>
<Spawn Id="DefaultRespawnPlayer" Event="RespawnPlayerKit"/>
<WorldInject Operator="Any"> <!--This is how you inject a StartCondition into an existing world -->
<World Id="Mars"/>
<World Id="Moon"/>
</WorldInject>
</StartCondition>

to

<StartCondition Id="Default">
<Name Key="DefaultStartCondition"/>
<Description Key="DefaultStartConditionDescription"/>
<PreviewButton Path="Interface/button_starting_standard.png" />
<Spawn Id="FuelTankInsulated" Event="NewWorld" />
<Spawn Id="DefaultLander" Event="NewWorld" Spawn Id="DefaultLander" Event="NewWorld" /> <--- here is the change!!!!!--->
<Spawn Id="LanderCapsuleSmall" Event="NewPlayer" />
<Spawn Id="DefaultNewPlayer" Event="NewPlayerKit"/>
<Spawn Id="DefaultRespawnPlayer" Event="RespawnPlayerKit"/>
<WorldInject Operator="Any"> <!--This is how you inject a StartCondition into an existing world -->
<World Id="Mars"/>
<World Id="Moon"/>
</WorldInject>
</StartCondition>

should also work for other starts if you change it at the specific section for example under
<StartCondition Id="VulcanDefault">

i hope this helps.