Backing up my Mac

You can still use TimeMachine to back up your iMac:

https://support.apple.com/en-us/HT201250

Take care and do make backups.!

iCloud is not meant to use as a backup tool: it’s a sync service.

Here is how iCloud works and how to set it up:

https://www.apple.com/icloud/

https://support.apple.com/en-us/HT208681

I think you misunderstood things: it really is possible to use TimeMachine to make backups. It works on Catalina as it worked before.

If your LaCie drive is not recognised by your Mac, use diskutility to reformat it. choose te reformat it in Mac Os Extended (journaled). if you don’t know how to do it, just ask.

If you don’t see your Lacie in Finder:

• Click on Finder, Preferences, sidebar and select external drives
• click on Finder, Preferences, General and select External drives

• connect your Lacie to your Mac
• open diskutility on your mac
• make sure you select the lacie on the left side of te window (under Extern): don’t select your internal hard drive!
• click on Erase
• give your Lacie a name, eg backup drive. Choose as format MacOs Extended (journaled)
• click on Erase

I've read somewhere that it is possible to backup two Macs to one external drive but I've no experience with this. Please put a new question on this forum.

Besides that: I would connect the external drive directly to a Mac to backup instead of using a wifi-connection