Constant freezing on AMD® Ryzen 7 1700 eight-core processor both Ubuntu 19.10 & 20.04 with 4GB GeForce GT 730/PCIe/SSE2

Hi, I have read through many similar issues in Google searches, none mention my particular configuration however I have seen lots of references to issues with Ryzen processors and Linux, mostly older posts, is this still an issue or should I be looking elsewhere?

My system was running well until about 2 months ago under Ubuntu 19.10, then it began to freeze, sometimes irrecoverably, only solution, hard reset. Since then I've changed graphics cards, re-installed Ubuntu 19.10. Storage is set up with a SSD as system disk with a 650MB EFI Partition, 447GB Root Partition and 32GB Swap Partition being 2x System RAM. The Home Partition is on a 2TB HDD. I have Benchmarked SSD and HDD returning no errors. Most recently I performed a fresh install of Ubuntu 20.04, while the freezing is more of a long pause now, it is still very evident. I'm at a bit of a loss as to what else to try.

I would really like a clue as to what to try next. I was going to start changing SSD and HDD drives, but when I saw the number of past issues with Ryzen processors, I thought maybe I should ask this question here first. I built the system and it ran well under Windows 10. I don't use Windows when I'm at home so moved to Ubuntu 19.10 retiring an older AMD that had run faultlessly for years.

I hope someone can help me resolve this issue. I'm no coder, but I have learned to use the Terminal when I have clear instructions.

Thanks in advance, Chris.