Would recommend you pick up a basic SSD (solid state drive) from a reputable manufacturer, of 2x or greater the size of your internal storage. Plug that in and follow these instructions:
https://support.apple.com/en-us/104984. (You want extra room on the backup drive to account for old versions of files, which Time Machine will keep for you if you have enough room). You can get by with an older style mechanical hard drive, but I would recommend SSDs at this point for reliability and longevity.
But yes, this is a weird gap between iOS and macOS. We have iPhones with storage sizes rivalling those of Macs, but there is still no native iCloud backup tool on par with what you have on iOS and iPadOS. It would actually be completely in Apple's best interest to develop this, as it would drive increased demand for iCloud storage. ¯\_(ツ)_/¯