What's the best camera for non professional photographers? ?

Depends upon the type of photos you want to make.  Pros often use multiple models depending upon their needs if there isn't one model that does what they need.  For example if a pro shoots landscapes and low-light hand held work, they'll want a high resolution camera like a Fujifilm GFX-100 for landscapes and high-ISO camera like the Sony A7S for that type of shot.  They often will have a much smaller and compact camera for carrying around town.  You wouldn't want to bring a $10,000 GFX-100 to a party because it's too big, heavy, and you'd likely be worried about it getting stolen.

Look at the mirrorless cameras since DSLRs are being phased out for the preferred mirrorless systems.

An entry-level model (i.e. the least expensive) like a Nikon D3xxx series or a Canon T series will be just fine for any beginner.  Getting a mid-level body like a Nikon D5xxx, D7xxx series or a Canon 80D will likely be more camera than you need today, but it will allow you to grow into the camera as your skills improve.

Professional as in you still are serious with photography but not earning money through it? The best camera for you are the same ones the pros use. If you meant not really caring about settings and stuff but just shoot pictures then your phone would perfectly do!

Get a Bridge camera. Bridge means one lens with a vast range, so you do not need to carry heavy lenses around.
Look up 'Best bridge cameras for 2021' on Google. The range is fantastic. I can shoot close ups of a butterfly on a flower, or the surface of the moon, all with the same lens on the camera. Mine is a Nikon. 

A non-SLR digital camera with an Olympus lens

There isn't one unfortunately. Look at a full frame for sharp and crisp images. I had a Canon 5D but sold it because i wasn't using it enough to justify the price.