It's not currently possible to explicitly set an Exclaimer Cloud - Signatures for G Suite client-side signature, on mobile devices. However, if the mobile devices own signature is disabled in the client / mobile application, then the client-side signature will be applied in transit. The following behavior applies:
If you have configured a client-side signature, this will be applied, by G-Suite, to messages sent from the iOS Gmail apps (the client-side signature is applied at the bottom of the message chain).
The client-side signature will not be visible when composing the message, and the above all occurs prior to the messages being routed to Exclaimer Cloud.
The client-side signature will not be applied. Instead, the message will route to Exclaimer Cloud, and receive a server-side signature (if configured).
Gmail Mobile Website
If a Client Side signature has been configured through Exclaimer, and you use the Gmail Mobile Website, then the client side signature will be applied in G Suite prior to the email being routed to our service.
This signature will be applied at the bottom of the message chain and will not be visible when composing the message itself.