Apple's advert for Catalina/Sidecar on their website is potentially misleading.
Catalina adverts on Apple's website are potentially misleading, possibly breaking Advertising Standards, the small print 5) (click the number to get small print), states all that is required for Sidecar (using your iPad 6th/7th + Pro models) is an iPad with pencil support, but what it doesn't say (found elsewhere) is that it's only certain models of mac that will run Catalina, also support Sidecar. (i.e. a subset of Catalina capable macs)
The thing that raises an eyebrow here is that the somewhat averagely spec'd Intel MacBook Air 2018 and the Macbook 2016* (with integrated graphics) supports Sidecar, so it seems, Apple are making strategic marketing choices rather than it being a performance-related reason for being excluded.
Also, the cheapest 9.7'' 6th Gen iPad can be paired, the latest 2019 5th iPad mini can't.
The days when Apple computers 'just worked' (without hidden quirks) are long gone, using/supporting this crud is a real headache.
See the support page for more into:
* Macbook 2016 - 1.1GHz dual-core Intel Core m3 processor (Turbo Boost up to 2.2GHz) with 4MB L3 cache