Apparently in order to use the macOS built-in scanning interface (easily seen in Preview, Image Capture, or the Printer/Scanner System Preferences) the scanner must have TWAIN or ICA drivers. I’ve got two Brother all-in-one laser printer/scanner/copiers, both “supported” with Catalina drivers, but not TWAIN drivers so they theoretically only will scan using Brother’s scanning software (sounds like Fujitsu here, doesn’t it?). I don’t know if I should have looked at Cannon or HP instead, but I did see with a web search some people with Cannon AIOs also having problems.
The older Brother AIO, a DCP-L2540DW, actually continues to scan with the Brother TWAIN driver when the system is upgraded from Mojave which was upgraded from High Sierra. Brother only has TWAIN drivers for High Sierra and earlier. I consider myself lucky as it’s obvious that if I were to do a fresh install I’d be out of luck.
What brought up the issue for me is I just bought a DCP-L2550DW (the newer, replacement model) for my wife. Then I find out that it never has had drivers supporting TWAIN, and even if I tell the OS to use the 2540 drivers, while it still prints, it doesn’t see the scanner (no TWAIN).
I could buy Vuescan, but apparently it doesn’t act as a TWAIN driver so still won’t be integrated. Or do I misunderstand Vuescan?
Surprisingly few people seem to have discussed this, so maybe I’m doing something wrong? FYI, I’ve rarely used the scanner on my Brother since I also have a ScanSnap iX500.