What is your recommendation on upgrading a Linn LP

If the plinth is nice keep it and maybe start with an Ittock LVII tonearm. Maybe some new springs. Linn makes too many upgrades. Diminishing returns do not always makes sense and are seldom worth the costs for what you get out of it. I've rebuild 3 Sondeks. New motors and belts can help too. The rest is pretty much cosmetics. Good luck.

I owned an LP12 with an Ekos arm, and the one thing I learned in owning this table is: Tune up. Have it set up by a reputable Linn dealer and he will be the best to make recommendations of what should be done. If you don't have a dealer locally, contact Rick at audioalternative.com, he will advise you how to pack and ship the table to him. Once he has it he will access the condition and needs to return the table to optimum performance. Then once you have it, you can start deciding if it needs a new arm, power supply, keel, etc. But that is where I would start, the suspension on the LP12 is crucial to performance and it really needs to be done by someone that does it all the time. Just my opinion of course.

A standard Linn table is fine. The Linn upgrades are IMHO way to expensive. Better to safe you money and buy something else.

Actually many Users who can remember back to early 1980s models find that the Valhalla version has much to recommend it.
(The Valhalla is no longer supported by Linn so you can't buy one now BTW)
One way to get close to (or better) that performance is to buy the Hercules II AC PSU. It is an external supply so fairly easy to implement.

The only thing I would say about the Hercules is that it can be sluggish on startup and you should give the platter an assist to get it up to stable speed more quickly. Once it's running of course there is no need to switch off the motor - just flip LPs while the engine is running.
It's an art best perfected without a felt mat (use a Ringmat instead because it doesn't stick to the LP) ;^)

The 1980's Linns are keepers. I'd do whatever I could to keep mine going. I am original owner of my Linn Axis that continues to deliver the goods. I'll be keeping it still as long as is possible.