As a guest User you can not add Apps/Tabs to the channel. if the Site Owner/Admin adds the Lists app to the channel and Guset in same tenant then guest user can use the Tab/App. Teams admins control the features available to guests.
Here some guest capabilities provided by teams-
https://learn.microsoft.com/en-us/microsoftteams/guest-experience#comparison-of-team-member-and-guest-capabilities
Here some document for reference-
- https://learn.microsoft.com/en-us/microsoft-365/solutions/collaborate-as-team?view=o365-worldwide
- https://learn.microsoft.com/en-us/microsoft-365/solutions/plan-external-collaboration?view=o365-worldwide
Thanks,
Sayali
If the response is helpful, please click "Accept Answer" and upvote it.