I use
https://mycollection.stanleygibbons.com.
I get access to all (non-specialized) listings across all their offerings.
I also use the Michel and YT online offerings.
All offer monthly or yearly plans A LOT more affordable than Scott - plus a real search engine.
If interested, I can send some screenshots. I believe there are also trial periods.
The only hardcover I've had to order are the FACIT Special Classic and Norden, and the latest Maury (although there's a Kindle offering for this last one.)