To begin with, when picking a domain name for your brand, there are 2 questions to answer and two options for each of them.
1° do you want to buy an existing aged (ideally non-dropped) domain with some SEO authority?
OR do you want to create a brand new domain?
2° do you want a domain which features one or more relevant keyword(s) OR do you prefer a fully original domain name? You can also be subtly creative around existing keywords.
It all starts with a name...
Your domain name is usually the first semantic contact people will have with your product or service. It should be catchy, easy to memorise and relevant. Your domain name is your marketing ice breaker. It should kickstart the conversation around your brand.
A good balance of meaning & rhythm
In most cases, you want your domain name to convey the idea that you're (easily / quickly) solving a problem for your potential customer.
I like the name NewsletterOS.com given by an entrepreneur to his Notion-based digital product helping you to create and run a successful newsletter. The domain name fully encompasses the core promises of his product, i.e. serving as the Operation System of your email efforts.
You could imagine a series of alternatives with a comparable semantic impact, also added as a relevant qualifier at the end of a domain name:
e.g. (you can buy the ones which would still be available): thecookingbible, easymarketinguide, SEOhandbook, thebloggingnotebook, automationsecrets, adconversiontips, etc.
Some of those suggestions include a second qualifier (e.g. "easy"). You don't want to go crazy and end up with a 50-letter domain name but two to three syllables work fine both in terms of meaning and rhythm, providing a nice effective prosody.