Apple Silicon MacBook Pros come with an SD slot. There are some MicroSD adapters (I use a BaseQi 303A) that are flush with the case - so flush infact that they are a bit hard to remove. Those are excellent for TimeMachine backups.
To add more context, I only use TimeMachine for the use case "I deleted something I haven't committed to Git and want to revert to the state of 1h ago". My real backup is offsite + encrypted (Arq + paid GDrive).