Going from MM to MC

I would go with the Linn so you know you’ll have a cart well -matched to the arm. No, you certainly can match different brands and they may work fine, but if you stick with Linn it’s one less thing to think about. And you got the Linn 3-point mounting, which is another thing you don’t have to deal with.  Simplify your life. You’ll be happier for it. 

Absolutely not! The Ortofon and the Lyra are far better cartridges. I would lean towards the Delos here if the naked cantilever does not scare you. If it makes you nervous the Ortofon Quintet Black is also an excellent cartridge. Good choices.

For any MC cartridge, check the recommended impedance loading, see if your SUT or Phono Stage provides a good match.

Your Phono Stage's Impedance via Potentiometer is a splendid feature

i.e. the Delos:

• Recommended load directly into MC phono input: 97.6ohm ~ 806ohm (determine by listening, or follow detailed guidelines in instruction manual)
• Recommended load via step-up transformer: 5 ~ 15ohm (step-up transformer’s output must be connected to 10kohm ~ 47kohm MM-level RIAA input, preferably via short, low-capacitance cable)
• Recommended tonearms: High-quality pivoted or linear (tangential) tonearms with rigid bearing(s), adjustable anti-skating force, preferably VTA adjustment

Delos uses a boron cantilever, much better than aluminum, a spec better than Ortofon’s Sapphire, read Ortofon’s text

The Linn has good specs, except Aluminum Cantilever

Ortofon’s separation specs are NOT GOOD, you mention separation, the channel separation is listed as >23db. The other two are >30db.

..........................................

My choice, far less cost, was/is the Audio Technica AT33PTG/II. It’s separation is >30db; it’s tight channel balance (very important for imaging within the wide separation) is 0.5db

I have other cartridges, my friends bring theirs here, so far it’s loved by all.

I wore my stylus out, AT trade in sold me new cartridge for half price.

Of course they have some higher priced, different technologies, but the separation/imaging specs are the same as the AT33PTG/II.