From tube phono pre to GS phono pre

Welcome to the forum. Just because a ground wire is connected does not mean the turntable is properly grounded. The way to check for grounding continuity is to use a multimeter. There can be issues with turntable tonearm designs where something seems like it should be grounded but in actuality it is not. Ground loops can also occur in audio systems and those require troubleshooting.

Interference and noise from interference are complex issues and really need to be looked at on a case by case basis. As Graham has noted, such issues often occur when using LOMC carts but can also happen when using common MM carts. Too many sources of interference near the turntable, poorly shielded arms, poorly shielded cables, etc. can cause problems.

Re: the tube hybrid phono preamp, I've always thought those things were a bit of a gimmick. To me they exist mainly for marketing purposes because they give the fiddly audiophile types something extra to fiddle with (e.g. "tube rolling"). If you look at those circuits the tubes are not actually doing a whole lot. It's also possible they will be more susceptible to interference than a good 100% solid state design.

I would encourage you to try a GS phono when you can, but I would get your "system hygiene" re: grounding and interference sorted out first so you can properly judge the product.

FWIW I dealt with RFI in my system before I got my GS phono. No longer an issue now but when I made the decision to buy a new turntable a few years ago I made sure I set it up in such a way that interference would be mitigated. The turntable has a metal tonearm, the cables are properly shielded, and the phono preamp is sited away from the turntable and "smart" devices. I also do not use powerline internet adapters and have placed my wifi router as far away from the turntable as possible.

My 2 cents.