wow, a dual xeon e5 2690. Have you tried to put it for rent to the render farm? I think 50c of euros/8hous is kinda low for such multi-core CPU like that and maybe render farm will pay you better. Remember mining is about min max the profit vs electricity. Of course, you can mine for fun or depend on circumstance, that's the best you could do.
Hmm I didn't know it would ve possible to rent the cpu power, but I guess I lack the network connection to do it
I took the liberty and make a simple check for the rental price of a dual xeon e5 2670 (your is 2690) server at irendering. The price is $1 per hour. That's quite a good price and better than 50c euro after 8 hours of mining. It's really up to you. There is also another way to make money from having multi core CPU, you could try setting up multi android device to running apps, games aka bot farming.
Now, I know this kind of stuff doesn't sound like crypto mining or related to the mining section but from what I see, many mobile games right now have NFT features or play-to-earn crypto so it is actually related to mining only a bit different as it will require your inputs over time. Think outside the box and you will find a better way to make decently profits from your CPU, don't have to strictly to the traditional mining process.
Wow very interesting stuff here. Thanks for the inputs. I have some work to do here hehe.