time machine

"If both drives are not in the Exclude List, then Time Machine is backing up both drives."

Adding a drive (item) to the list will Exclude it from TM backups.

How are both the Apple and Samsung SSDs formatted?

How and what are you using each of the SSD's for?

(one for macOS and one for your user data)

(one for one macOS and one for another macOS)

At this point I'm not certian why TM is not backing up both of your internal drives.

If the Time Machine backups were started before the Samsung SSD was installed, then that could be the problem and I would try setting up new TM backup on a different external drive or erase the current TM drive and start over.

If both drives are not in the Exclude List, then Time Machine is backing up both drives.

Hi TheMrRedPanda,

Thanks for using Apple Support Communities. We understand you have some questions about Time Machine. We're happy to share some information to help.

You can find some great information about Time Machine and how to change your preferences here: Change Time Machine Preferences on Mac

Thanks

By default those both should be backed up by Time Machine.

How big is your Time Machine backup drive and how much space is used for Backup?