Thank you for your detailed response - I actually just edited my post just above yours - but I now read that command functionality has been disabled by Apple anyways!
When I have restored my Mac in the past, or set up a new Mac, Ive always used my clone as part of the setup process and migration assistant copies everything across, just like it would from a TM backup. Ive found it to be very quick.
Ive never actually used it to boot off of it and clone back across to the internal drive - just as a means for Migraton Assistant to copy everything across - has always worked well for me this way.....
I just wanted to use TM as a more up-to-date option, since the clone always relies on me manually creating it, but don't want to use my internal drive space for any backups at all.....
So, if local snapshots are created with automatic backups, if I manually create Time Machine backups instead, I assume local snapshots are no longer created? Considering the TM drive is a NVMe in my dock, which is always connected anyway, created a TM backup manual would be quicker and easier then a clone, which needs to to connect another external drive and wait for the entire process to complete. I don’t need hourly backups - one at the end of the day would be fine, so seems a manual TM backup may be the way to go for me....
My understanding is that local snapshots are created mostly (but not exclusively) when the Time Machine drive is disconnected or unavailable. They are used sparingly when the Time Machine drive is connected. (This is not well documented, so the exact mechanics of it are a bit of a mystery.) Local snapshots are always created in certain situations, such as when installing a macOS update (on Sierra or later).
You are correct in that the "disablelocal" option for tmutil was removed in Catalina, so this is now out.
If this helps, you can remove all local snapshots by disabling Time Machine backups temporarily; just open the Time Machine system preference, turn Time Machine off, wait a few minutes, then turn Time Machine back on.
More to the point, can you explain why you're concerned about local snapshots? They're just a part of the operation of macOS and should not cause any trouble. Time Machine is meant to be a "set it and forget it" backup that you never think about. That is one of its major advantages. Manual backups tend to be forgotten about and go out of date, thus end up being no backup at all. With Time Machine, it's just there in the background always doing its job, always up to date, maintaining a backup history of every file revision going back as far as your backup disk's space will allow.
In effect, local snapshots do not actually use space on your internal drive; they do use space in a literal sense, but because macOS automatically purges them (silently) if the space is needed, you will not know that they are there and they should never get in the way of your work.
Having a separate clone is a good practice and I'm not trying to discourage you from doing this in addition to Time Machine; redundant backups are important, given that any drive can fail at any time. I clone my Time Machine backup drive every week and I'm actually planning to buy an LTO drive and start backing up to tape again (which I have not done at home in over 15 years) to simplify offsite backup media rotation. Perhaps I'm something of a throwback.
