How to compensate for Facebook compression of Covers? Extremely low quality

I use Photoshop to create social posts for Facebook and other platforms. (Used to use Spark too.)

Facebook has a new algorhyth that now compresses all Covers regardless if they're sized correctly. On PS I've tried saving as PNG and webP and they are equally horrible once posted. **The images are scaled appropriately and are less than 100kb.

I read a blog suggesting to double the size so that when it compresses it won't look as wretched.

I did this, it looked passably better but it wasn't scaled properly and was too tall.

Rather than continue to play with the dimensions, has anyone found the silver bullet?

I'm an old school designer who learned during the days of exacto knives, rapidographs, and hot wax. I try to keep up with the tech side but for me it's just so that I can design. I know enough to be dangerous. lol.

I used to post regularly for a client on FB and it always looked crisp and sharp. I was horrified when I posted and it looked muddy and heavily pixelated.

I'm on an iMac 12.3.1 and up to date with CC PS.

PS BTW, it looks atrocious if I do it on the new Express. It looks horrible post production before I even posted so I immediately jumped on PS. That's another post how Adobe killed Spark, I used to create great images for social platforms and now they're all blury and muddy. It was fast, easy and fun. Quality now is horrible, features have been removed, blah blah blah.  😞